D16y5 D16y7 D16y8 different piston part #?
 

It seems like all the AFTERMARKET pistons rods etc for the y8 list being compatible with the y5 y7 as well; however, looking at the OEM part # for the piston, piston ring, and bearings of the y5 it differs? Why is this?

Heres the breakdown of what ive found out.

D16y5 and D16y7 both have the same compression (i forgot the #) but y8 has different compression.

Each one actually has different part number for the piston. Why is this?
Piston ring part numer for y7 and y8 at the same though. y5 different. Why is this?

Connecting rod part # are all the same.

Crankshaft all the same.

Bearings part # for y7 and y8 are the same. Y5 different.

Has anyone ever done a rebuild on a y5 or build up on a y5? non minime