I have two transmissions that I was going to combine and rebuild into one good one. Once they were both fully apart, I noticed some things that I don't know.

One case has an 8 GM 591615 (the one from my truck) and the other has 6 GM 591615 (extra trans).
Not sure if there is a significance of the first number when deciding which case to use.

The mainsheet in the 8 GM 591615 is stamped, WT242-2C. My truck is a '51 and I think the '51 trans has a WT242-2B mainshaft.

I guess what I'm asking is; is there a problem with mixing parts and or case?

Does anyone have the specs for the transmission components so I can hunt for the correct ones?

Any help from Bolters would be great!