Conway,
The original LeMans 427 engines were designed with different cranks and rods as Ron said above, plus they had other aluminum weight saving parts. They were designed to run at 7,000 RPM for 24 hours instead of 500 miles like the NASCAR version which was heavier. I don't have all the specifics but I think there is a Ford website that has all that information. If I can find it I will post it. I had one engine that came with LeMans rods in it and changed them to the regular NASCAR rods as the LeMans rods were lighter but just didn't seem to stand up to daily driving as well as the heavier ones do.
