ZR 2 C 4 Corvette.523.C.I.D. Installation notes One of the most important things to do is to check your bell housing mounting surfaces for "Parallel" ...even though it is a very high quality Lakewood S.F.I. Ballistic, we found that it was out 30 thou., side to side, probably because of the welding to add the "Ears" for the custom ZF-6 mounting, but regardless, it should be verified anyway. Milling this to perfect at the best local machine shop (the owner built his own Top-Fuel rail car, so you know he cares) cost 50 bucks... What a bargain! The previous owner had implied that it was "hard on clutches", no wonder! Can you imagine how far out and how much stress there would have been on the input shaft/pilot bearing/clutch/flywheel assembly, aprox. 8 inches forward, with 30 thou off parallel back here? This simple, inexpensive blueprinting operation could have saved untold expense and down/repair time to the previous owner(s). . .