[Bruce Robles]

Smash
You can bolt a trans from a 5 bolt Bellhousing to a 6 bolt Bellhousing and visa-vera. I had an original GT-350R that came with a 5 bolt engine. As the amount of races grew we built an extra engine that was a 6 bolt block. Everything was the same but the Bellhousing, same headers, same clutch linkage ect.
Our later engines were in the 375-390hp. range and the best clutch we ever used was a Genuine Ford Hi-Po Clutch, Period! Tried alot of different aftermarket crap, Hayes, for one, and none of them preformed any better than the Ford.
Most of them had heavier springs in the pressure plate that only made it harder to disgengage the clutch especially after many many laps on the track. The extra spring tension required that the clutch equalizer arm (bell crank) be beefed up and gusseted more, (ours was already beefed up) which cause interference with the headers and made it a pain to install. It had to be massaged a bunch so it would work.
Most aftermarket clutches are re-built factory jobs with a fancy paint job, that's all. Don't fall for all this hype and spend good money where you don't need it.

Good Luck
By the way, I have a Hi-Po 289 Long Block with 4 bolt mains and original cast iron race heads, interested?

Bruce Robles