Salley builds a ZZ502/550 that has your cam in it plus hand ported ZZ502/502 heads (110 cc). I bought one and added a BG 870 cfm speed demon carb. I have not fired it yet ..........

Billsbird is right on their 630 HP 502 crate motor as well ...........

For an extra $~2500 you could add a roots or centrifugal supercharger and tack on up to 200 hp more fairly easily. I am looking at a Procharger blow-thru unit right now running at a modest 6 psig for my 9.6:1 502 to bump up another ~150 hp. But I will probably get over it ............

kitz