I failed to mention that a Magnum engine will require an electric fuel pump as it does not have the components to drive a mechanical fuel pump. This is a dealbreaker with some. A Magnum engine will be a little more work such as outfitting it with the LA timing cover so you can run the LA V belt and pulleys. 273,318, 340 and 360 (All LA) exh manifolds will work on the Magnum heads. The path of least resistance-closest to plug and play for you would be another LA engine. If you could see and hear a used one run before you buy- that would be easiest and cheapest. Clean it maybe do valve cover gaskets and the oil pan if its shows signs of leakage. Paint it up nice and beautiful and install. A member here may be within driving distance and have a good healthy used engine for sale.