The cab is identical. The frame is heavier gauge on the 3/4. Wheelbase for 1/2 116", 3/4 125". Bed length 1/2 6.5', 3/4 7.5'. Tires 1/2 has 4 ply, 3/4 6 ply. Gearing 1/2 4.11, 3/4 4.57. Springs 1/2 8 leaf, 3/4 2 stage 7 or 8 leaf.
Brakes. I don't have specifics on the 48, but the 1/2 had smaller brakes than the 3/4.
Tranny. 1/2 had either 3 speed column or 4 speed floor with one-piece enclosed driveshaft. 3/4 had only 4 speed floor with two-piece driveshaft, front half enclosed, rear half open.
Differential - 1/2 had a semi-floating differential, where the axles are loaded with weight of the truck. 3/4 had full-floating, axles carry no weight, only driveline (power) load.
1/2 ton 6 lug wheels, 3/4 8 lugs.
If you are trying to decide on which to get, I would recommend the 1/2 ton, mainly from the standpoint of availability of wheels, tires and suspension upgrades. Front suspension packages are available for the 1/2, not for the 3/4. Rear end swaps are easier to make, with many possiblities. Wheels and tires are also easy to obtain.
