The OP has a 1988 K1500 with a 10 bolt rear end. Upgrading to a 10.5" FF axle seems like overkill to me. May as well buy a heavy 3/4ton . Upgrading to a 9.5" SF would be worthwhile and that would be much easier and more than good enough. (I've never done it as my K1500 came with the 9.5") He could add a leaf or two to the rear springs if needed. Braking is always a concern when carrying a truck camper with a 1/2 ton truck. I've done it and you definitely have to drive slower and allow much more stopping distance.
Typically, the tire pressure on the door sticker is for maximum GAWR/GVWR. 50 PSI gives you a load rating of about 2205 lbs per tire. 65 PSI gives you about 2600 lbs per tire and 80 PSI gives you about 3042 lbs (for a 245 size tire, 265 will get about 3400 lbs.)
So, to get the rear GAWR of 6084 lbs (typical for 3/4 ton or SRW 1 ton) you need to have 80 PSI which gives you 2 x 3042 lbs = 6084. You certainly don't need 80 PSI in the rear tires when running empty or even with a moderate load.
Typically, the tire pressure on the door sticker is for maximum GAWR/GVWR. 50 PSI gives you a load rating of about 2205 lbs per tire. 65 PSI gives you about 2600 lbs per tire and 80 PSI gives you about 3042 lbs (for a 245 size tire, 265 will get about 3400 lbs.)
So, to get the rear GAWR of 6084 lbs (typical for 3/4 ton or SRW 1 ton) you need to have 80 PSI which gives you 2 x 3042 lbs = 6084. You certainly don't need 80 PSI in the rear tires when running empty or even with a moderate load.