Check with Sean Dempsey. Sean is a FWC dealer in WI. Sean used to have a ~2002 F-350 Long Bed with a Grandby as his personal truck/camper rig. don't know if he still has the rig. I bought my Hawk from Sean. A fantastic guy to deal with and camp/ride motos!
In so far as carrying the camper in a 2002-2003 F-250....
I had a 2003 F-250 7.3 (Crew, short bed) and installed the Old Man Emu 2" suspension kit with overload spring. The kit is spec'd for F-350 weights. My Hawk is in the bed full time hence I wanted the overload spring. I can't begin to describe how much better the ride was after installing the OME kit. The ride improvement was simply remarkable. Absolutely worth every penny!
I installed the kit because the OME springs would sag with just an 800# payload. I didn't want any sagging or leaning once I installed the camper and traveled off-road to dispersed camping sites.
I like my 2016 F-350...but sure do miss the simplicity of that 7.3 engine!
I'm considering replacing the factory rear leaf springs on the new truck with Carli springs to improve ride quality. This will decrease payload some, but, I'm never loaded near max payload with the camper so not an issue.