there is no way that thing controls your transmission. the original ECM might be hanging around somewhere being piggybacked, or maybe your transmission isnt a 4l80e at all? you say you assume it's computer controlled. how many wires and sensors are on it?

you haven't even mentioned if the vehicle runs badly with the current setup, someone might have already done an alright job tuning it.

i say learn to tune the DFI system. i love antique crap. it'll be really easy on your wallet... if the software only runs on dos or something, who cares? people throw computers like that in the garbage.