You will exceed your GVW with almost any camper. With bumpers, fuel and people I'll bet you weigh close to 8k lbs so less than 2000 payload.
However, I'm on the side of staying within axle and tire limitations. GVW seems unrealistic.
I would look for an 8-10' non slide camper like a Lance 915, 920, 1010 or similar.
If you want a slide, look for an arctic Fox 811. Nice camper made for SB or LB. You won't find many used LBs as they seem like more of a SB camper. Still heavy, but very little overhang on a LB so truck will handle better.
I'm sure Buzzcut will check in soon. He has a similiar truck with a heavier camper but with appropriate mods.
I had a Lance 981, 9'10" full wall side which weighed over 4500 lbs ready to camp. I carried it on a DRW and it was a load.
Good luck.