Good luck with that as there Pro Top Line heads. They basically copied a small block Chevy exhaust port...They make headers for that head but I’m pretty sure they used the outer threaded holes...

 

I found this article 2nd pic which is the head I have and the jba headers look the same port style and gasket like the head are u sure they are a Chevy type port?

 

As long as the port is in the stock location you should be good. They copied the port of a Chevy head because its a better port design..Your going to have to try it to see if they fit or not..

 

The dilemma of running a good head in a 65/66 mustang. What are your goals for the car. If you just want the cubes of the windsor and aren't looking for top horsepower you could get away with the short tube headers and a well designed exhaust system. If you are looking to maximize what you have you may end up paying some money for headers that work. Another option is to buy header flanges that work with your heads and have them welded onto what fits.

 

My goal at this point is to just drive the car cuz it’s been a lot of work and is totally disassembled but yeah I would like to get as much power out of motor as I can with that said it seems like every other header has problems I seen headman has square port and oval port headers so I need square port but not sure if regular square port is good because these head ports seam wider than stock there tube design are all like the ones I have and spark plugs are way to close to the tubes 1/16 to maybe 1/8 on two cylinders seems like the jba 1653sjs header is the best unless I ding the tubes in or notch the shock towers I think I need to get the jba header gasket and see how it fits before spending $800. Pics are stock head vs mine port size seems smaller horizontally to me by the pic

 

You basically have close to a race port on your head. You might try a straight plug boot with some of the heat sleeves they sell to protect them but you may have problems with sealing if you use small tube headers with the narrow bolt pattern on your heads. A set of large tube headers using the wider bolt pattern will seal better but be even closer to the plugs.

I have copied a link
Other Parts

to a forum with lots of pictures and discussions on this matter. The guy who posted all of this is a member on here as well. I would search 65 mustang and 351 on this site as well.
If I went to all the trouble to build a dart blocked windsor with good heads I would take my time and find good headers. I wouldn't choke it with short tubes.

 

You basically have close to a race port on your head. You might try a straight plug boot with some of the heat sleeves they sell to protect them but you may have problems with sealing if you use small tube headers with the narrow bolt pattern on your heads. A set of large tube headers using the wider bolt pattern will seal better but be even closer to the plugs.

I have copied a link
Other Parts

to a forum with lots of pictures and discussions on this matter. The guy who posted all of this is a member on here as well. I would search 65 mustang and 351 on this site as well.
If I went to all the trouble to build a dart blocked windsor with good heads I would take my time and find good headers. I wouldn't choke it with short tubes.

Thanks for info yeah I don’t want to but am getting frustrated at this point and really need to drive it but I know speed cost money! I talk to FPA header guy and he said he doesn’t make a set for the 351 in a 65/66 at all unless I notch the shock towers

 

I am not sure my link is good. Go to Ford Muscle Forums and search 351 and headers.

 

Call FPA, expensive but will fit and perform.

 

Yep called him already he doesn’t make anything for 351 in a 65/66 unless I notch the shock towers.

 

I talk to RHS who makes the same head and the tech guy gave me part number felpro 1487 for header gasket port height 1.62 width 1.42 i stenciled on the head with blue pen the measurements with veneer calipers. So on the height I would only have 1/8 inch contact on top and bottom that just does not seam right. The gasket is for the 3inch bolt pattern for a 1 3/4 header tube. Anybody know About a gasket that fits better the head I have port height is 1.32 and width 1.30 The head that RHS makes now that has same exhaust ports is the pic part number 35011-01

 

One suggestion I would make is to post on another site like the Corral or the yellow bullet (tech section only) where there are more drag racers and you might find people more familiar with trying to find a gasket for a big port like this. One thing lots of guys do is just seal it up with high temp RTV sealant as opposed to using a gasket or with a marginally sealing gasket. A lot of guys swear by it.