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'66 coupe to fastback conversion progress

32011 Views 161 Replies 36 Participants Last post by  gt350sr
Working on my '66 fb conversion last night- got the quarter panel mostly removed and cleaning up the edges for panel replacement. I still need to remove the inside edges of the original quarter, but my new plasma cutter made quick work of it! I also had to melt out the factory lead filler from the seams to get to the welds. At one point my neighbor walked in into my shop and asked if I was getting high! I was so engrossed in what I was doing that I didn't realize the entire shop was filled with a smoky haze from all the grinding! lol

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wow, and i thought i had some work to do on my coupe. that is some serious restoration sir...looking good.
More progress this weekend. Right side done- was a bugger as I found crash damage under the replacement quarter panel that was on it. The po had used about 10 lbs of lead to raise the corner up around the trunk lid. I got the new one installed, and was very impressed with the quality of the panel- it actually fit the contours of the side scoop pretty well! These are the 'better' panels that I sourced from NPD.
Got the left side off now, getting ready to install the quarter skin maybe tonight.

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Since this is now a build thread- thought I'd add a few pics of where I started from. The coupe was a vinyl top car that was severely rusted through underneath the vinyl. The fastback was the opposite- the roof was the only thing worth saving as even the dash was rusted through. It had been sitting in the swampy area of a junkyard in southern Iowa and got flooded out every spring. Since I had to replace the roof of the coupe anyway... well, you get the idea..:wink:

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More progress last night- got the left quarter mostly installed. I still need to finish weld and grind the upper edge but it's looking like a car again! Nala gave me the paw of approval :wink:

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Looking good! Definately a lot of work involved in doing the conversion correctly but it is turning out nice! What are your plans for the car engine/drivetrain wise?
I've got a 351W stroked to a 393 ready to go in, back by a built C4 trans. The front suspension will be slightly upgraded stock with disc brakes, the rear I've got an Exploder rear that I'll be narrowing down to fit. It's got 3:73 gears, 31 splines, and discs already, so a nice upgrade. The body will be mostly stock, simply adding the Shelby side scoops and a '67 style Shelby fiberglass hood. I haven't picked a color yet, leaning towards black but we'll see how good my bodywork turns out! Inside will be stock black vinyl, adding a Dakota digital dash and matching glovebox door, 4 point roll cage, and rear seat delete. Should be a fun car to drive :wink:
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Sounds like that will be one nice ride! I too am going with the Explorer 8.8 3.73 limited slip rear. I plan to narrow just the long side and use two short axle shafts to center the dif and get the correct width.
Sounds like that will be one nice ride! I too am going with the Explorer 8.8 3.73 limited slip rear. I plan to narrow just the long side and use two short axle shafts to center the dif and get the correct width.
Exactly what I'm doing. I scored an axle for $25 from the local yard- just need to start cutting!
wow, that's a hell of a project. looks good! how much, besides the obvious, has to be changed for the conversion?
left quarter after finish grinding- 1 low spot due to a previous dent, but otherwise came out pretty good. Should take barely any filler to smooth out nicely. This was one of the 'better' quarter panels from NPD and it fit very well. Also pic of the hood I'll be using..

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wow, that's a hell of a project. looks good! how much, besides the obvious, has to be changed for the conversion?
It's actually easier than it looks. The A pillar cuts on my donar roof were cut straight through, so I chose to sleeve the pillar for strength. On the last one I split the A pillar and lapped the pieces over the whole length.
In the rear I cut the quarters off for access, then drilled out the spot welds over the inner fender liners, along the inside floor where the trap door attaches, and the trunk hinge plate. Behind the door jambs is even easier- drill out the spots up the door post and the entire roof lifts off. I prepped the coupe frame the same way, then set the roof down on it. There are actually dowel holes along the door posts for alignment- probably the same way the factory did it. I used bolts the same diameter and the roof pretty much sat down perfectly- not much tweaking needed. Welded the inner bracing in the same locations as factory, then from that point is was the same as hanging quarters as if it were always a fastback. I bought the good quality panels from NPD and the fit was spot on. So far it's been pretty straight forward, should have the body done this weekend and start hanging the suspension.

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What about all the interior bracketry? How are you going about placing them? Nice work! I look forward to doing the same thing, however I am spending the $$ and getting a kit from Mustang Depot. My car needs all new metal so this is the time to do it.
I got off easy on this one as far as the brackets go. The ones attached to the roof section stayed in place, so I can attach all the interior trim. I kept the floor brackets off the donar, but will be installing a roll bar, so access to the rear seats was limited. Instead I'll be replacing the seats with the flat Shelby style seat delete tray. On my other conversion I was able to measure off another fastback for placement, and weld the floor brackets in place. IIRC I had to remove the coupe seat floor tabs and reposition them for the fb seat.
Narrowed the 8.8 Exploder rear axle last night by 2 7/8". Got it welded up, just need to dress it yet. The 2nd shorter right side axle slid right in like butter- fit perfectly. Next is to scratch up some spring pad mounts and get them welded on at the right angle!

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Looks good! Any tips or tricks or the cutting/welding? I am going to tackle the same project shortly. Please let me know which perches you end up using.
Looks good! Any tips or tricks or the cutting/welding? I am going to tackle the same project shortly. Please let me know which perches you end up using.

The main thing was to get as much of the complete fb roof as you can. Drill out or cut around the inner bracing that attaches to the wheel tubs and floor pan area. On the quarters, cut a few inches below the body line and give yourself enough to weld new ones to. In the doorjamb area, the flat spot above the striker is different- the coupe has a slot for the rear window to travel through, the fb is flat- no hole. Be sure to cut below this area if possible to transfer it to the coupe. Inside that doorjamb and behind the interior quarter trim- bend down the tab you'll see and drill out all the spotwelds leaving that inner steel structure attached to the roof. THIS PIECE IS VITAL to making alignment correct when reattaching to the coupe substructure. You'll notice a 1/2" hold near the tab you bent- it's for aligning the panels with a dowl pin or bolt later. You can see what I'm referring to in some of my earlier attached pics. On the rear you'll want to keep the small 'bumps' in the trunk lid opening where the lid bumpers rest- fb's are in a different location. You can cut to the insides of these and transfer them over as well, or fab new ones if need be. You can leave the coupe ones in place, but they won't align. the lid will still work and seal on the rubber molding, but might not sit just flush with the body. You'll also want to keep the rear edge of the quarter that tucks under the quarter extensions- that will also make alignment much easier. In the front on the A pillars I recommend drilling the spotwelds, splitting the pillars and lapping them back together- much stronger that way. On this car the roof had already been cut straight though midway. I stubbed the coupe the same way, then added steel sleeves between the sections and plug welded them solid. If you take your time and think things through before cutting/welding, it's not as hard as it looks. :wink:
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Here's a pic of the door jamb area I mentioned. I just finished welding a filler plate in and sprayed primer on it for now. I still need to go back and clean it up better, but it was getting late last night..well, the beer was tasting too good that is >:)

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A little more progress- got the roll bar welded up and set in place, and all 4 floor patches done. The PO had covered the thin floors with black silicone, laid tin on top, then smoothed out the goo that squirted out the bottom through the pans. From underneath it looked like perfectly solid floors, but when I peeled the carpet I found the surprise! $27 per patch and all solid now. Also got my spring perches from speedway for the Explorer axle swap. They say they're 3", but they fit the axle perfectly- no trimming needed. PN# 54585090- here's the link Speedway Weld-On Spring Pad for 3 Inch Axle Tube
They also sold me their matching 3" x 8" Ubolts which also seemed to fit just fine- even though the axle is supposedly 3 1/4"... And no- they're not welded on in that position! :wink:

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