Foy,
Somewhere you have an "unladen" weight label on your truck. Take that and deduct it from your GVWR, that would give you your payload, It will probably be more than Longhorn1. Without doing some digging, I would guess that a '02 F250 would have a GVWR somewhere around 9200lbs. Your F350 probably has a different front axle, hence the rear spacers and has larger brakes.
Historically, brakes also change as you go from a 1/2 ton to a 3/4 and to a 1 ton. I do know that there has been brake size changes between SRW and DRW 1 ton pickups.
My truck's "wet weight" which is often referred to (I think) as curb weight or unladen weight and which for Federal income tax purposes is known as Gross Vehicle Weight (GVW), that being the weight of the truck alone, full of fluids (and fuel?), but without passengers or cargo, is right at 7,400 lbs. I've read that the 7.3 liter diesel with its normal attachments weighs 1,200 lbs on its own. I don't know if the second battery under the hood is part of that 1,200 lbs or not. I know for certain my GVWR is 9,900 lbs, and with the wet weight/curb weight/GVW where it is, I believe my payload is 2,500 lbs. The way it's normally configured, which is with a heavy fiberglass shell, an inside-the-shell toolbox, and a host of tools and outdoor equipment, I've weighed it at 8,240 lbs at the local landfill. Loaded up for a weekend trip and certainly for a haul to Montana, it's got to be pushing 9,000 lbs. Add about 300 lbs of tongue weight from the hardside A-Frame popup camper and I'm pushing the GVWR and I might be a tad over it.
Unless what I faintly recall reading years back was wrong, my front drive axle is a Dana 50 and the rear is a Dana 70. If the same reading was correct, the '02 F250 diesels had the same axles, brakes, drivelines, etc. The point of the piece I read was that for '02, at least, the only difference between an F250 and a SRW F350, each with the 7.3 diesel, was the spacer blocks in the rear and higher-rated OEM tires.
Foy
