yes it is possible , I recommend using closed chamber heads to kill detonation with quench , 915 or 516 are the closed chamber castings , with larger valves & smart port work & a good cam 500 gross hp is possible . we did a mild 440 build with iron heads , cam & 6 pack & made over 310 RWHP on a Mustang dyno through iron exhaust manifolds so that would have been closing in on 500 gross hp .
I charged $500 for porting , valves & machine work should be around $500 , cam & springs / retainers 500-600