Before I start I searched to the ends of the earth to find an answer for this so if its already on here I apologize in advance.
I have a 80 720 with a L20B the trans is slipping and the engine is weak at best. I don't care about speed I just want a reliable truck that will run and drive. Having said that I already had the driveshaft modified for the air ride and don't really want to drop another 500 on that. Do I rebuild the L20B and 3N71 or swap to a Z or KA engine with their respective transmissions (auto preferrably)? If I swap, and this is more something Id like to do, what modifications will need to be done? ie. motor mounts, trans mounts, firewall, etc.