I assume you have the TH350? Those are pretty stout transmissions in stock GM form, even better with shift kits. You can upgrade the torque converter to one from the TH400 for a bit more robust unit. Are you planning on putting lots of HP through it? One nice upgrade you could do is to go to a 700R4 for an overdrive. The 4L80E requires a computer to run it, which can add undo complexity to a simple solution.

Just my $.02


1987 B250 - Painkiller