my old 500 CI blue thunder engines made 648 HP and about the same in tourge !
B class engines...but solid and dry ! @ 6500 RPM

i got 540hp/570tq pretty easy on a 522" (overbored 502). Port work and cam selection will make all the difference in getting you where you need to be. I have it for sale if you dont want the hassle of building your own.

As mentioned tho your heads will hold you up a bit. I made 695hp with just a little 489" w/9.7 cr but that had worked Supercat brodix heads (still small ports) and the right cam.

any advice on cam?

you can look up on here a build that was done to an hp500 to make 600. They might have used the 741 cam but not sure. Its been awhile but they covered every aspect of the build. If you dont mind doing the extra up keep go with solid lifters so you can spin that motor up. It will give you a few extra ponies and handle the RPM.

Call Bob Madara at 585-654-8583....... no need to look any where else and adjusting your valves will be a 1 time thing.