It would be easier to drop the engine and and transmission on the cradle to swap out the transmission. A swap of that nature should be done by an experienced mechanic because lots of stuff needs to be replaced including the ECM. Since it is a high milage car swap out the engine at the same time.
www.twinlakesfiero.com www.v8archie.com depending on what engine you want and how much $ you want to spend. You should be able to get the car in like new condition for under $10K