Each of your selections have good points: They are both common, therefore have parts available and so each one would cost about the same for acquiring, building, repairing, or maintaining. I think the issue comes down to what you are going to do with it. If you are lifting for use in the mud, then you are talking about full suspension redesign for mud tires, and if you go mudding, you will want the extra torque the 360 has over the 318. Not that the 318 cannot have torque, but it is usually easier to build torque into higher displacement motors. If you are just lifting for looks, or will not get into hairy mud too often, the 318 will suffice and be more fuel efficient with less displacement. For many years the older generation of hot rod racers who were into dodge swore by the 318, calling it "bulletproof," and "the toughest engine ever made by any company." There are lots of similar raves for the 360, but not as famous as the 318.