All aluminum case PowereGlides out of a V8 application are alike. The L6 PowerGlide is made with smaller parts (narrower, lighter, and smaller in diameter internals) that makes it too weak to last behind a V8.
An aluminum case PowerGlide has the rear tranny mount located in the same place; and it is the same over all length, for easy interchange, in place of a Saginaw manual transmission, or a Muncie manual, or a TH350 or 200R4 automatic transmission (the 200R4 uses the TH400 rear transmission mount location). If you only want four out of the seven bolts in the bell housing to bolt up you can also include all of the BOP transmissions as well. BOP stands for Buick-Olds-Pontiac; though it includes Saturn and Cadillac engines. Chevy is the only GM product that has it's own bell housing bolt pattern that differs from all other GM cars.