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.
Theoretically the shorter rod will keep the piston at TDC for less degrees of crankshaft rotation, which will be more pump gas friendly. That was one of the reasons I went with a 6.535" rod.
