But I suspect that you've got a mismatch of connecting rods here. Different combinations of cranks and pistons often create such problems, because the wristpin hole in one type of piston may be in a different position to accommodate a shorter or longer connecting rod. This is a frequent complication to putting stroker cranks in American V8 motors -- they usually require custom pistons or rods. Some ultra long stroker hot rod motors require pistons with the wristpin ABOVE the oil rings in order to avoid excessively short rods, which create problems of excessive connecting rod angles at mid stroke -- the Ford 351 Clevelands were pushing the limits on this issue even in stock form.