Hi all, it's been a very long time since I last posted anything on this forum, but I was getting the itch to get back into the classic mustang game. My question is- How big of a difference would it make if I used a toploader made for a 390 in my 1969 Mustang with a 351W? I have only owned slushboxes, but I'm trying to understand these toploaders. Other than the tag, I dont see much of a difference. Any help is appreciated- Thanks ahead of time.

 

you just need to make sure you have a clutch and drive shaft to fit the input and output shafts .. a friend used a 428 4 speed behind a 289 years ago .. had to use a 428 clutch i think .. bigger shaft ..check you pilot shaft bushing also

 

Thanks for the response. The best I found was on wikipedia, where it gave me a longer length for one in particular that I was looking at. Apparently 1969 and up the 4sp toploaders go from 26" to 29" in length. Input shaft and output splines remain the same. I am guessing it may be due to a longer tailhousing? Are those fairly interchangable (assuming I could find one)? Otherwise, I guess I can get a driveshaft meant for a 390- equipped car.

 

I had a similar problem with my 1967 Mustang. The engine is a 1968 Shelby GT 350 (302). The C4 transmission case is from 1968, but I believe the guts or just the tail shaft is from a 70's model (don't know how that happened). This caused some problems with the driveshaft. The driveshaft was about 2 to 3 inches too long. We took it to a repair shop and they cut a section out of it and rebalanced it for us. It ended up costing less than getting a new driveshaft. I wouldn't recommend getting a used driveshaft, you never know what could be wrong with it or how strong it is anymore.

 

If you have a driveshaft (or 2 if doing a swap) with the right yokes, a custom link shaft is very cost effective.