[Bigdav160]

The problem with your plan is GM diesels had 4L80e transmissions behind them not 4L60e.

IIRC, the electronics are not interchangeable.

There are stand alone aftermarket controllers and I've read about using GM computers as stand alone controllers.

Why don't don't just have your 700 rebuilt and upgraded? It wouldn't worry me a bit that it is an '84 model. People just make a bigger deal out of it than it really is.