As a follow up to my original post what challenges will I face if I find a 400 that was originally mated to an automatic trans but I want to mate to my 4 speed Muncie trans? Are the splines the same size? Any other parts I’ll need?
There are 2 problems that you could encounter.
(1) SOME cranks, in auto trans engines, were not machined to accept a pilot bearing or bushing. Some were. Obviously, you need a bearing or bushing for the snout of your manual trans front shaft.
(2) Some of the late '70's engines had cranks with a smaller centering ring on the crank. I think the early cranks were 2 3/4", & the later cranks were 2 1/2". PRW sells flywheels that come with an adapter ring, so that you can use their flywheel on either crank.
But, if you find an engine with a 2 3/4" centering ring, your flywheel will work. I assume you could use it with the 2 1/2" ring, if you could buy an adapter ring. A good machine shop could probably make one. Don't know if anybody sells one or not. Guessing that PRW does not sell their adapter rings separately.
Checked online. You can buy an adapter ring from a Pontiac guy on Ebay.
The splines of a manual trans front shaft would only be affected by the clutch disc. So, you'd need to choose the correct disc for your splines, regardless of what engine is used.
The splines on the front shaft of an auto trans go inside the torque converter.
