I'd want to do some very detailed checking on combustion chamber shape, gas flow, and piston-to-valve clearance before I'd try to use anything taller than a flattop piston. The main advantage to the 307 stock piston is that it's a drop-in replacement for the dished 250 piston, same weight, bore size, wrist pin diameter, and compression height. I believe it's also available as a hypereutectic alloy which rivals a forged piston for strength, and it has virtually zero thermal expansion.
The first high-compression 250 I built went into a Nova 2-door, and it was a real hotrod. My student did a very precise weight-matching job, down to 1/10 gram on everything that moved, plus a good port & polish and a 3-angle valve job with stock-size valves. We didn't dyno it, but he and another student with a Firebird with a Pontiac 350 in it used to race to school frequently, 20 miles of 2-lane highway, and neither one could outrun the other. I think they both got a very expensive speeding ticket one morning!
Jerry
