mamboitaliano,
You must be referring to the clutch and pressure plate...huh! There are two different types of release fingers on the pressure plates that may require you to use a long or short throwout bearing, but any two 'flywheels' wouldn't differ enough in thickness to be noticeable.
Flywheels can be drilled for different size clutch assemblies, and some are drilled to accept several sizes.
Maybe I don't understand the question.
Stuart
