Streetrod, Drew here. I realize that you're looking to modify (e.g., stroker, turbo) a DOHC Aviator engine in your new '03 Explorer. I noticed that the '06 + 4.6L SOHC with three valves (variable cam timing) approach 300 hp (290-something), and have cast iron blocks (maybe more durable for high mileage rebuild). While I know nothing about their ability to be souped up to 500 hp, I do know that the aluminum-block version of the '06 + Mustang 4.6L v8's (of which there should be plenty around) landed on Wards Ten Best Engines list for three or four years. Question: DId you consider--or have you heard of--anyone upgrading a third gen 4.6L explorer to a 3-valve, vct engine, to get the substantial performance boost? Presumably you'd need a to use a the '06 PCM and wiring (e.g., for vtc), so maybe that's a non-starter. Nice looking '03 you got there . . . .