[LastToy]

Question on the difference. I've done many searches but I don't have the answers I am looking for. Other than the semi-float, larger front diameter, different rear caliper (larger piston), and different caliper bracket, is there a difference on the spindle and/or upright? StopTech offers two different brake kits for regular E46 M3 and E46 M3 with ZCP package. If there is no difference in the spindle/upright, why would they offer two difference products? Also, AP Racing sells two different brake kits for an E46 M3 and a Z4 M Coupe. I own a Z4M and am trying to figure out why an Essex AP Racing brake kit for a M3 will or won't fit my car. I already called and asked Essex and Bimmerworld and they don't know the answer.

Thank you.
J