I personally don't see it going over that number. He needs a lot more camshaft and the heads/intake will need port work. FWIW, I did a 408 Cleveland based on those heads and intake, with 10.5:1 compression, and a 248/254 @ .050" cam, .670-.680 lift and it made 575 hp at 7000 rpm here. He would have to pick up 50 hp over that and the compression difference would make it for a lot of it, but the cam isn't nearly big enough for 30 more cubic inches. My guess is that his engine would peter out at around 6400-6500 with the camshaft he has.
However, remember, that you can make anything work. I like the over-square engines for race motors, not because an under-square motor won't rev, or won't make power, but it's often easier to make horsepower with a larger bore because you can fit bigger valves into the heads. Also, a short stroke engine is easier on the rings and bearings because of piston speed and the size of the crank that you're trying to spin at high rpms.
Will an under-square long stroke engine make horsepower and rev? Yep. It just takes a little more work and planning to make it do so.
I think in the overall scheme of things, to hit the numbers and rpms he's wanting to hit, he's probably better off with another combo, especially if it's a factory block. I would do an aftermarket block, 4.155" bore or larger, and a pretty short stroke....3" or 3.250". Turn it to the moon and add a ton of head/intake/cam/compression.
I build as many small blocks as I do FE's, so if he has a question or is stumped on something, feel free to give me a call.
