Do some googling on this. Not sure about trucks, but the 94-96 B-bodies this is covered quite well. The earlier 4L60Es will not work but I think you can use a 96/97 and just swap the 95 valve body. Keep in mind in 98 they went to a different style case. Not sure I would waste time with a used 4L60E unless there's documents to support it was rebuilt recently. I would opt for rebuilding YOUR 4L60E. I would opt for a reputable online vendor (Probuilt Automatics) even after almost 30 years the local guys still can't seem to get it right (my experience).

https://www.impalassforum.com/thread...b-body.232098/

TPI with your TBI heads will be an excellent combo for low end torque. I believe Fast355 did this swap over a decade ago on TGO. I also believe your PCM can be modified to be setup in batch fire mode (same as the TPI ecu).
https://www.gmt400.com/threads/tbi-t...on-mpfi.39486/