[Jack21]

Flycutting pistons is used for adding piston to valve clearance when necessary. It's effect on CR is minimal.

If you're pulling 450 ponies out of your 351W, that's about as good as it's going to get with a street driven car, and keep it streetable. In a Cobra, you'd have little competition.

A '69 Mustang, however, is not a Cobra. It is a full size and heavy car. If I recall, these things come in at 3,600 - 3,800 pounds. The hotter ones in '69 sported 429's, and even then had trouble keeping up with the Chevies, and Mopars.

For a heavy car you need torque, and to get torque, you need displacement, supercharging, or both.

Dollars wise, the easiest thing to do is add the stroker crank, and pistons. If you want to go hunting big blocks, dial your CR in at about 8.5:1. Otherwise, go about 9.5 - 10.0:1 for pump gas.