Several have mentioned that the op would be better off going with a 5.9 magnum. But I haven't seen anyone mentioning that he needs to be sure that the one that he gets has a cam that works with a mechanical fuel pump, if not he'll either have to change the cam or use a electric fuel pump, a added expense. That he will need a torque converter for the 5.9 as it's balanced differently than the 318, another expense that he probably hadn't planned on. And the last time I checked the magnum heads are limited to one intake manifold choice. The op mentioned that he has 3.21 gears, nothing mentioned about that he'll need to change the speedometer cable gear so that the speedometer and the odometer will read correctly, unless he's already done this. Isn't it true that the 5.9 and the 360 require different motor mounts then the 318 does? I'm not sure about the harmonic balancer, but would it require replacement as well because the magnums have computer controlled fuel and ignition systems, if so that's another expense. I don't know if the flex plate is different from the 318's. The oil pan, oil pump pick up tube have to be swapped out as well.