The 4200 figure in the shop manual is gross weight with 6.00-16-6ply tires. The 4800 figure is with 6.50-16-6 ply tires on the rear. That's the mfg. suggested weight limit for a fully loaded truck. Read the note. .....includes the truck chassis with lubricants, water and full tank or tanks of fuel, plus the weight of the cab or driver's compartment, body and special chassis and body equipment, and payload.
By the way, the series numbers have nothing to do with weight.
