Your compression is still only around 8 to 1 or 8.25 to 1 at the most.
.http://www.wallaceracing.com/cratio0001.htm
I been around these for years and know you can not pick up compression so easily. Swapping pistons or gasket thickness will or get you a cc or two, and a simple valve job can loose you just as much.
I just restored a '71 HO engine last fall for a 100% stock, numbers matching Trans Am, and I can tell you for a fact, it did not have dished pistons. Pontiac used four valve relief flat tops.
As Jon pointed out, tuning a tri-power is tough, even tougher on a 455. Unless yours uses the larger center carb, I wouldn't even attempt it. Dad tried for a couple of years to get one working and never could, and tuning is what he loved to do. The Quadra-jet will run circles around the tri-power, thats why GM went to them.
Joe
