Lots of places just list the 84/85 kit for 79-85 pickups. The front springs are the identical, the rear springs are the same length and will bolt in place, but I've read that the centering pin is just slightly different. If I remember right, it will move your axle back about half an inch back. ARBUSA is good at answering questions, I'd give them a call if you want to know for sure.
If it's a full kit, the springs and bushings and shackles should all work. I'm not certain about the steering dampner or shocks.