Ed, as far as I know, the 5 speed will work out of an S-10 if you shorten the input shaft to match the length of a 3 or 4 speed. It worked in my 54 GMC with 302. It will bolt to the bellhousing. The Camaro 5-speed will work with no modifications if shifter location is not a concern. The Camaro shifter is about 7 or 8 inches farther back than the S-10. The Camaro transmission rear mount is also at an angle because the trans was mounted at about a 30 degree angle for floor clearance.
The Saginaw 4 speed with OD is a 4 speed with an overdrive unit added to it from a Saginaw 3 speed. It works well also, though you have to find a Saginaw 3 speed with OD (very scarce and probably expensive if you find one)and make the modifications to the trans. There was an article in Hor Rod Magazine in about 1974 on how to do this. There is a lot more to it than the article said, though. I built one and ran it in a 1964 Ford 4WD pickup with a strong 400 SB for probably 10 years. I really liked it.
The 4 speed with 4th gear as OD is a New Process aluminum trans that was used in Chevrolet and GMC pickups from 1981 to maybe 85 or 86. They are pretty hard to find, though. Since this was a New Process built by Chrysler Corp, it was apparently also used in Dodge pickups and some cars also. The bolt pattern to bolt to the bellhousing would be different and probably the input shaft. Those problems can possibly be worked around, I don't know. I also ran one of these in the same pickup for a while, but the synchronizers were worn out and I liked the electric OD better on the Saginaw better so I put it back.
Overall, in my opinion,for your application, I think the S-10 5spd would be best for several reasons. One is weight,another is shifter location. The 5spd has a top mounted shifter, on either the S-10 or the Camaro. The others both use a side shifter which might take up your master cylinder room in a roadster like you're planning. The saginaw also has a governor and a shift solenoid that stick out-one on each side of the trans. Also it needs wiring with a relay etc.
Another possibility I just thought of. In the mid 70's some of the Chevy Monzas used a 5spd. It was aluminum with a top mounted shifter. It was behind the Vega 4 cylinder so it probably wasn't very strong. I don't know much about them, though.
Well, this is pretty long winded, but I hope it helps. Joe
