Did you check the ATF level with engine idling in neutral? It could be several quarts low. Was the trans working when it was last driven?
If a torqueflight is driven a few hundred miles with not enough kickdown it can and will burn up the clutches.
If it needs rebuilt get a shop that does many old car trans jobs. So get with some drag racers or a car club to see who is good in your area.
EFI? We got this far without it. Do what you want.
I like carburetors.
