Rebuild 5.7 or buy something else?

VVT engines are still in their infancy regarding tuning. Keep in mind that the Challenger that put out 454whp also had headers and a full aftermarket exhaust and a cold air intake. Plus an untold number of hours on the dyno tuning out every last drop of power for promotional purposes. I have not seen or heard of anyone else making that much power with the 274 cam.

Aftermarket stroker short blocks go anywhere from $3-4K. Even if you do all you can yourself you are still looking at around $3K for machine work and the cheapest stroker kit.

If I were in your shoes, I'd disassemble the short block and inspect the bores to see how bad they are and to check for damaged pistons rods and crank. That will help you determine how to proceed.

If the block and everything else look good I'd ball hone the cylinders and buy a rering kit with rings bearings and gaskets (about $400 on ebay)and put the stock short block back together. I'd have the heads cnc ported and get a healthy cam with a good timing set. You could have a 500 crank hp capable long block for about the cost of just a bare stroker short block.

But, if you want anything over 500hp, a stroker is the only way to go. I know of a couple making in the 620 to 650 range with the early (03-08 ) heads.

I hope this helps