I seem to have two different types of rear hub, the material thickness is the main issue. One is thinner but has a thicknessing behind the stud locations in a cross shape the other is thicker full width. Do Ineed a matching pair and does anyone have one spare?

a design revision probably. Considering the tiny weight of a 7 to that of a sierra full of shopping and passengers, I'd not bother changing it.

drum/disc differences...?

ABS/non ABS differences...?