Mate 67 /6 to 72 tranny

I would rebuild the 72 tranny. No sense not to since your engine is rebuilt. You can do it, I did (at least the A-413 torqueflite in my FWD minivan, essentially same). The manuals are step-step. If you can't find A-904, you can download free an A-413 manual from Neon tuner sites, and I expect "close enough" for a "banner rebuild" (gaskets & clutches). Don't dig past the clutch packs. If you pull out the over-running clutch in the bottom, it gets tricky to reinstall w/ the little rollers & springs. When reinstalling, use the front parts from an earlier transmission and those are small enough to ship affordably.