I would say the intake valve bitch slapped the piston more than once!

Don't think I've ever seen one actually wear a groove in like that......especially as fresh as it all looks.......

Obviously, you're going to be going with dished pistons and not those Domed Speed Pros. Check out Diamond or Probe, personally. Cams, a lot of ways to go. On a mild build I would look at the old Crane Commander 292 or the Comp 301 Extreme Marine hydraulic grinds on a BBC (They still make them, under a different tag number nowadays, but work well with smallish blowers I'm told) Hopefully some of the expensive hardware in that engine are salvageable.
Good luck, keep us posted.
Ray
Edit, you should be able to find pistons to get the compression down to a more reasonable 7.5-8.5:1 (Low maintenance pump gas engine) even with your small chamber heads. Dunno if they're open or closed chamber, what you have. 990's are everywhere and reasonable compared to the $2k for aluminum if you don't have the change for them, but depends on what blower intake you have as well going from Oval to rectangle ports........but 650 HP should be easily attainable and on the low end of what you actually end up with, depending on blower condition, etc .........
