The stock six pilot bearing will fit the AMC V-8s perfectly, as the crank flange is the same '72 and up. The 304 will be ok with the t-5, but a 350 or 360 AMC will break it quickly unless you baby it. The AMC conversion requires a new right side frame bracket and special CJ only engine block brackets that are still available new from the dealer, for around $120, or used at a wrecker. The stock 6 radiator will work ok if it is a 3 row/AC type. The V8 fan shroud is still available new and is recommended. A 2 row would probably be OK in the northern areas though. A chevy conversion requires the hose outlets to be switched to the opposite sides, easily done by any good radiator shop. Expect around 12-13mpg if the V8 is close to stock. The AMC swap is very easy, and the result looks and acts like the factory did it! The Chevy is more work, but the parts are cheaper. In either case, be sure to get all of the accessories with the engine, as buying all the brackets, bolts and fittings adds up very quickly. Hope this helps, good luck!