sorry USAnumber1, but given how miniscule the CV angle change is with ~1-2" of torsion bar crank, I'll chalk up any subsequent trouble more to the vehicles being ~15yrs+ old with well over 100kmi on them. That goes for CVs, wheel bearings / hubs, all of it. I've been posting about all the 'refresh' and tweaks for the GMT800s in my own build topic and my 'Hey Vortec Guys' topic for some time.
In fact just recently I was posting about the degradation of the torsion bar adjuster key crossmember mount bushings and the few options for repair or replacement. And how the system is designed with vertical range of motion / pitch in the torsion bars as the lowers move. And how a bit of crank on them does f-all to really change things as you are still operating the front suspension within the mechanical limits of the upper and lower control arm stops.
As long as you set things so it isn't riding on the stops, you retain much of the original ride. Ride only gets bad when you really crank them to the max and essentially lay the upper arm on the stop. And then you get a crappier 'lever arm' of movement on the lower, with it's steeper angle AND you get the crappy ride on the return bounce as the uppers hit their stops too soon.
So I wouldn't say one could get more than 2" out of a torsion adjustment change without wrecking the ride, with stock arms. And if your torsion bars are fatigued, you may not even have enough adjustment in a stock key to even get it up that high.
factory vs Rancho 'leveling' key. You can see the leveling key gives you about a 1/2" advantage on the adjuster bolt depth. So if you are starting with a really worn out ride and can't afford the $600+ for new torsion bars or the bother to pull some from a wreckign yard, the $40? for the keys is an easy short term fix. But you should really swap out or upgrade the torsion bars to do it properly.
eta
pgs37-40 in my Vortec topic, talking about the failure of the mount bushing and various ways to correct it or improve it and my first pass at doing so as a proof of concept. Most folks with GMT800s here probably don't even know this mount is failing on their vehicles. Won't know until it fails enough for the crossmember to rap against the frame mount, metal on metal.
I'm replacing my lower control arms next month, with fresh bushings and ball joints and probably crafting some shaved down polyurethane bushings for that above pictured mount. There's nothing wrong with the rubber I put in there, yet and I suspect not for a long time, the way I don't drive it hard off road. But I want to try re-working the polyurethane version of the same fix and maybe offer them to folks here that need a similar fix.
The "proper" way to fix that mount is cut the whole metal mount off the frame and weld on the new one with its apparently cast-in-place bushing & bolt sleeve. Or by a replacement mount and cut it apart to excise the bushing subassembly and try to press it into the original mount ring, on/under the vehicle. And you have to drill / grind out the old mount the same way I had to so I could insert my modded control arm -style bushings, anyway. A lot easier just to put in the control arm style inserts.