I've been considering the possibility of a later model rear for my 3/4 ton GMC, also. Have any of you also involved with the 3/4 tons noticed the rear ends under the mid 80's Chevy chassis cab duallies? The full floater axle hubs are the long type like the original rear in my 52 (as compared to the shorter full-floating axle hubs on the rears from the 3/4 - 1 ton pickups of mid 70's to late 80's). The outer tire on the chassis cab rears appear to be nearly in line with the front tire, instead of a full tire width further out as with the dually pick-up rears. I'm wondering if this rear might not be a little more narrow than the later pick-up rears. I see these rears most commonly under small school busses on the C30 chassis. Every time I find one standing still long enough to meassure, the traffic light changes and there I am, laying in the middle of the highway with an outstretched tape measure, looking like a durned fool!
I did notice a few of these school busses in a local salvage yard yesterday. When I have a day off and the yard is open, I'm going to get over there and get some measurements on one sure not to drive away. Just a few thoughts I figured I would toss out there for consideration.
