Are you wanting a 4L60e? I recently bought a 2wd 1998 4L60e core (removable bell, 6 bolt tail) for $75 from a tranny shop here is SATX, ordered an ATSG manual, and built it myself. Their really not bad. It was my first tranny build and it went smooth.
Between parts, tools, manuals, Advanced Adapters VSS, installed and driving, I might be in it for $650 or so. $300 of it was the AA kit to get VSS and mate up to my NP208.
I went with Alto red eagle power pack frictions, beast shell, .500 boost, vette servo, new planets, and a few other new hard parts, transgo reprogramming kit, etc. I’ve got about 3k miles on it so far and couldn’t be happier.