Well they did make suburbans with the 6.0 and 8.1 on 2500/3500 frames, and ford had the diesel 7.3 and 6.0 excursions. And i have seen the late 90s suburbans with diesels, ex govt vehicles I believe with manual hubs and vinyl floors
The 6.5, much of a turd as it was, was popular enough in the Tahoe's. Particularly the 2 door variants.
But boy, was a shite motor. Leave it to fucking Detroit to cock up a simple thing like a 180hp V8 diesel. International pulled it off for fuck sake.
Manual hubs on a late 90s chev would be pointless, as the axle is actuated between active and inactive at the center, not at the hubs.
Hubs being the lockout are a Ford, and Japanese thing, mostly. Ford loves their vacuum hubs (like Toyota), others used an automatic mechanical hub (Nissan/Isuzu)
The 8.1 'burb died in late 06, as did the 8.1. when they went to the new body style in 07, the 6.0 was the only HD gas motor chev had. The 8.1 was dragging down their stock fuel economy ratings and wasn't a huge seller.
Oddly enough, chev sold a 3/4 ton Avalanche (yeah, the weird unibody looking thing) with an 8.1 as the only engine option. I've never seen one in person. 4l85, 14b rear, whole works.
As for the frames, for some time, both Chev and Dodge used the identical frame for 1/2, 3/4, and 1 ton trucks. Dodge started it for sure in 1994, and carried it through to the 4th gen redesign in 2008ish, to keep costs and tooling down.
Each just designed one frame and ran different running gear under it. Chev had to put a 2" body lift on their diesel trucks to fit the turbo under the firewall.
It got to the point where chev used the same engine bays as well, with the halftons/gas trucks having a large open space in the bay where a diesels second battery would go.