The most important thing to learn is how to build torque where your dad will drive it. Put a 600 hp cam in a 440 and it will be a pig till WAY PAST the fun driving rpm. Personally i would shoot for max torque from 2500 to 4000 rpm and don't worry about hp. It is a lot more fun to drive a car that will pin you in the seat at 2500 rpm than one you have to rev the pee out of. Things that improve torque are maximizing compression and timing, getting the jetting right, exhaust improvements, rear gear change( not too much though!) And as far as cylinder heads go, some standard port aftermarket heads with bowl work and a closed combustion chamber. Getting the piston to head distance to .050 or a touch less adds torque.