1/2 ton and 3/4 ton front axles are the same except the outer hub assemblies have 8 lugs instead of 6. Even the rotors/calipers/pads are the same. 78 and older used 3/8" banjo bolts on the calipers and 79-up used 10mm. Your front d-shaft will be the same but the rear may be different, if yours is short bed, 3/4 tons are long bed. I would get the rear d-shaft too, and expect to have it cut down at a driveline shop to fit yours (also depends on slip-yoke d-shaft or slip-jointed d-shaft). 14-bolt rear axles found on 3/4 ton trucks have different dimensions compared to 1/2 tons (10 and 12 bolts) looking at the centerline of the axle shafts and the length of the pinion to the u-joint yoke. You may want to grab up as much of the park brake cables towards the back of the truck too if they're any good. You'll also need the spring plate that the u-bolts go through to bolt it in. The u-bolts are gonna be about 1/8" or so bigger than your 1/2 ton stuff. If the guy torched them off grab the pieces of one so a spring shop can figure out what size you need. You'll also have to figure in the thickness of your spring pack(s), as well as any lift blocks you may be using.
