There was a member on here with a gold Duster with a boneyard 5.7 that put down 290 on a chassis dyno. I think it was carbed...
Trap speed calculators put my stock engine (+headers and Mod Man) at around 290 rear wheel with my Megasquirt setup. I'm still spinning the tires on launch, so it might have a little more in it that's not showing up on the time slips, but I do know that it runs side by side with my mom's 99 Vette from a rolling start. Given the weights of the cars and whatnot I figure it to be around 350 at the crank.
not exactly apples to apples. 5.7's in cars and trucks are all through automatic transmissions and generally turning 20 inch wheels. 294 rear wheel horsepower is pretty decent for headers and a mod man intake. I would guess it made 260 or less rwtq.
I've got an old 833 behind mine, so no overdrive, but with my 3:55 rear gears and a 25.6" tall tire I can pull her right up to redline without much trouble. My speedo ends at 120, but I was probably doing at least 6k rpm if not 6200 (the redline I set), so that puts it somewhere around 130-135. There's another gentleman here that lives in Germany and drives his hemi swap on the Autobahn with no troubles.
It's not possible to hit 500hp in a 5.7 without a stroker or forced induction