Can an AA SM420 adaptor plate and spud shaft for a 3-speed case be used with a 4-speed case if I use the 3-speed gears. I'm considering purchasing a SM420 with AA 3-speed adaptors and would like to use the 4-speed case out of my 76 with a set of 3-speed gears. Talked to AA and they seem to agree that the bolt pattern and bearing are the same. Only difference would be the 10 spline spud shaft. I do not have the adaptors to verify my hypothesis... <IMG SRC="smilies/question.gif" border="0">

Everything is exactly the same and the four speed gears should fit right in.

Sounds like the answer I was looking for, except I'm lookin to use the 3-speed gears with a 4-speed case. Either way, sounds like the spud shaft spline count is what makes the call.

Yeah, both cases have the same bolt pattern, only difference is spline count in the gears.