George, my 1925 Buick six ohv had flat head with piston coming up short of block to form combustion chamber. The top of bore was tapered above ring travel and one simply pushed piston home by hand, overbore did not affect it, a truly good idea at the time. A word of warning for people using the Meco style of ring compressor, keep fingers clear of top, i have seen some fingers nearly sliced off when hammer handle misses piston top and hits finger laying over top of compressor. A very common injury for the unwary. Regards Jack.