I would consult the pros on this...you want the squish clearance as close to zero as possible while avoiding piston/cylinder head interference and without raising your compression ratio. It's not as simple as just shaving the head a few thousandths. But if your dad can rechamber heads, then maybe you're set.
From Gordon Jennings regarding squish clearance...
"The clearance space between piston and cylinder head must be enough to avoid contact at high engine speeds, yet close enough to keep the mixture held there cooled during the combustion process. This vertical clearance between squish band and piston should not be greater than 0.060 inch, and it is my opinion that the minimum should be only barely enough to prevent contact - usually about 0.015 inch in small engines (with tight bearings and cylinder / rod combinations that do not grow, with heat, disproportionately) and up to about 0.045 inch in big engines."
Do some research on the net...you can check your squish clearance with solder and a micrometer. It's a good engine parameter to investigate because it can yield nice power increases. Theoretically, if you can reduce your squish clearance by 5%, then you're pushing 5% more air/fuel to the center of the combustion chamber, causing combustion of 5% more air/fuel, and raising your horsepower by 5% (subject to frictional losses).