Because the engine will be used strictly in a high-rpm racing environment, McLaren swapped the 502's stock, but nonetheless stout, rods and pistons for stronger, race-specific parts (stock rod and piston are in the background). A piston with a full floating wrist pin was desired (stock is forged with a pressed pin) because there's less friction load at higher rpm and the piston is less likely to be damaged if the engine is disassembled. The new pistons are from Ross and are the only IHRA-approved slugs for Top Stock. Per the rules, the wrist pin location is stock, but the location of the "ring pack" is a variable. As for the rods, they're lightweight, forged H-beams from Carillo, with mandatory stock (6.135-inch) lengths. Interestingly, there's no specific compression ratio limit in the rules, but with cylinder head restrictions, the new pistons will provide compression in the 9.8:1 area.