Oh, I know, you "can" build a 500HP EFI engine that has cruise, street, and strip tuning maximizing the detune for cruising. But, we are on a budget here right?
A 500HP engine requires transmission and rear end and suspension, brake, wheel, tire changes to hook it up . . . ca ching. Otherwise you have an unsafe vehicle.
I've got a 450HP/550LB.FT. BBO running off the CCC, fairly mild cam by big block standards, into just W/Z manifolds and dual 2 1/2 with high flow cats in my 442 getting 18-20mpg . . . should get better with the 3.42s I'm moving to. With the engine specs and internals I used and mildly ported Edelbrock Aluminum heads as built, add 900 EFI, cam, and headers I am approaching 600HP and can detune that to probably get better mpgs than I'm getting now. Right now, I just hope to drive it again period with the current power plant post rear end rebuild, body bushing replacement, frame box since I have to take the body loose to replace them, then BACK to the suspension and brake swap.
It sounds to me like the 16 year old really wants the 500HP and to spend a LOT of money in the process.
But, what will the adult do for just a budget cruiser? I'll be watching no matter what you decide . . . It'll be fun no matter what you decide?