Which can take the most abuse and rack up the most mileage? For me it's between the 2V 4.6 truck engine, and the 4V 5.4 Navigator engine. The earlier 4.6 truck motors (and 5.4s too) has aluminum intake manifolds, which won't crack like the car manifolds. I'd say the 4.6 is a bit longer lasting due to the shorter timing chains. Sparkplug threads are a concern though. The Navigator motor is more complicated, but the Navi heads had better coolant flow around the exhaust valves and ports than other modular heads. That makes them a popular swap for burn-out contest cars. Any other choices?