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I am restoring a 67 S-code FB that I bought without engine or tranny. I have a 390 to put in it, but am still looking for a 4-speed. The veh serial # is 7FO2S142148, with 3:00 rearend and trans code 5. According to a toploader website, the 390 4-speed cars of that year all came with 28 spline output shaft RUG-M transmissions. The slip yoke on my driveshaft is, however, 31 spline. Perhaps at some time someone had put a 428 or 427 in the car. Who knows. The yoke can be replaced easily enough with a 28 spline, but my real question for all of you smart guys out there, is will ANY 4-speed toploader (RUG-N, RUG-E, etc) with the correct mustang tailshaft work? I have passed up some decent buys on "small block" toploaders because someone told me that I needed the "big block" toploader (RUG-M or equivalent I think, but I don't think he meant the 427/428 compatible large input/31 spline output). What is the real story here? I could use some expertise here. Remember, that this engine will be rebuilt very close to stock, with only a slight step up in cam, punched .040, and with the original 67 C70F-9510 Holley carb. I am located in central Indiana. Thanks in advance for any help!
 

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Why not go for on overdrive tranny that will make your road miles even more pleasent, improve gas milage, and make life a little easier for that 390, while tooling around on Indiana roads. The Tremec 3550 with a shortened input shaft should pretty much bolt right into your '67.
 

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Shhh!! . . . don't tell anyone, but I'm running a small-block toploader behing my 390 . . .

A small-block toploader has a longer input (pilot bushing) shaft and must be ground down approx. 1/4 in to fit right. The big-block toploaders have a shorter shaft, so they can't be used behind a small-block.

Contact Mark at ToploaderHeaven. He's here on the forum, also, and really knows his trannies! He can help you out more than I can.

HTH,

Rick
 

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The RUG-M is a wide ratio 390 transmission. It has a unique tailhousing from a Torino and small 1 1/16 input and 28 spline output(I have one).
All big block Toploaders had a slightly shorter input shaft. You can put a small block tranny behind a big block, but not reverse..

Oh yea, Mustang toploaders are 24 inches long.
 
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