[Coley]

I think that Chevy standardized on coil spring/trailing arm rear suspension as the factory 'as delivered' default with the leaf springs as an option and I think GMC was the opposite.
If it is a C20- 3/4ton, either one should work ok with a camper BUT......it depends on the camper you are looking at? (ie: 8'? 9'? 10'? or??? and what its weight is).
Do you have any information off of the SPID in the glovebox? (H.duty rear springs? auxiliary overloads? or??? camper special options?).
Also look at the GVWR plate in the door sill.....does it say 7500lbs as manufactured or?
The leaf springs always provided a more stabil load when carrying weight but the coils could carry quite a bit.
The thing with a camper vs other types of loads is the high/sway element where you would notice the advantage of the leaf spring and multi-point load carrying stability.
My two bits.
Coley