351 head gasket thickness
 

hey i have a 68 fsbk with a 70 351 windsor.The engine bulder used later model pistons in my early model block and the pistons were sticking out of the holes 20 thous.
The work around was to us 60 thous. head gaskets.The motor has about 7000 miles on it and runs great but I think thier is more power in it .
The question is what is the thinnest gasket i can run with clearance problems.
here are some things i know about the motor:70 block out of a cougar,world products senior heads,speed pro forged pistons with a 130cc cup. valves 2.02/1.60. Don't know the cam spec but it is fairly mild not a lot of lift less than 500 hyd,1.6 ratio roller tip rockers

If any one could advise on best way to determine thickness it would be greatly appreciated