The only part of the install that's time consuming is ya gotta cut off your old spring seats and then weld new ones on your axle housing. the rest is no more than just changing out rear springs. If you need another 1 inch of clearance, its your only option.
Here are a couple of pics of my Duster with a '66 b-body 8 3/4. There is enough clearance for 275-60-15s with this combo of offset hangers, b-body rear and 5 or 5.5" backspace wheels. Tailpipes are close, my wife bought the Summit Racing 2.5" exhaust kit, I don't have the kit installed yet but the pipes will clear fine.
This is the front hanger, it's a beefy piece. It does require a clearance hole in the frame rail for the welded on nut for the spring eye bolt. I've reinforced this area (clearance hole) with a steel plate since this picture was taken, overkill I suppose.
There's no doubt that its not a 123 installation, but if you really want that big tire in there, your only other alternative is to move the springs into the rails and mini tub it. Now that's work. If you wanna play, ya gotta pay.
I didn't have any problems with my install. Clearance hole is a must unfortunately. I can get 255/60/15 on my early-a-body with plenty of clearance. A 275/60/15 drag radial would work if I rolled the lip and had the prefect offset. I don't see how there could be any significant strength difference compared to stock rear hangers. I have 2.5" pipes from tti but the 3" pipes will fit too....barely on the passenger side. No issue with the later a-bodies.
Oh and a stepped drill bit worked best for the clearance hole. Found this out after doing one side first with a small cut-off wheel. Cleaner smooth appearance.
I put mine in several years ago and besides drilling a hole for the blind nut on the front hanger, it's very easy to install. Using the offset is supposed to get you and additional .80 of an inch so figure out if that will work for you. I am running 15x8 steelies and had the offset adjusted by by .75" and am running a 275/60/15 on my '69 Barracuda without any issues with wheel lip (which I did have before).