[Short 3/4]

Late 70's C20 discs are pretty much a bolt on. Hardest part is custom bending the lines for the dual master cylinder. That said, the stock drums in the 3/4 tons are pretty big. In all my decades of driving these old trucks heavily loaded, the only times I really noticed the discs was if brakes were really wet, like after a creek crossing, otherwise no real difference. Of course if you learn to drive with drums you learn really quick not to ride the brakes on a hill or tail gate. You may even notice the truck stopping better with some weight in back. Those 3/4 ton rears are so big they tend to lock up if the bed is empty, so rear brakes are wasted.
I would do a high quality complete brake job, including radiusing the shoes to fit the drums, which makes a huge difference. Then put on the camper and see how she stops, you may be pleasantly surprised.
Good luck
Tom