i can see the 512 might be the better combo in a 440 block but not a lo deck. the 4.250 stroke in a lo deck requires a shorter rod(6.535) to keep the piston at 0 deck or in the bore. seems to me the 4.150 crank with the 6.760 rod and the 1.120 pin height would be better in a lo deck or even a 6.535 rod with the 4.150 crank and a 1.350 pin height would give a better rod /stroke ratio than the 512 with the shorter rod. im no professional here but i think the longer rod is the better deal.