I have a indy block 4.5 bore 4.375 stroke. My old setup had a 6.535 rod. The psiton was as jim said 1.258 compression height. It did work but the pistons did rock at the bottom of the bore. I am going with a longer rod this time around 6.7 and a 043/043/3 ring pack. Pic is of my old vs new piston. The new one is 1.093 compresion height.