On my 2007 Ford, the camper package was mostly a certificate in the glove box, because I had ordered all of the 'camper package' items as part of other options, such as an optional tire package or a GCVWR package, etc. One could go through an almost infinite number of pertubations upon ordering.
However, had I not already 'ordered' those items in the process, then choosing camper package would have included those items as a significant-cost item.
So you would need to either see 'camper package' as an option, or be clever enough to read the door labels and the VIN number to ascertain that the selected vehicle you are considering has the requisite equipment installed to meet your needs.
When I carried a 2400 lb dry weight camper on my 11400 GVWR F350 SRW I extended the bumpstops on the overloads so both ends would be engaged firmly with the camper loaded - that made the best improvements to handling. Loaded for a long weekend I exceeded the GVWR by 600 pounds.
My best advice is to not be overly optimistic on what you can comfortably carry, as things tend to weigh more than expected and handling isn't as good as hoped for when over the load ratings.
I now carry a 1350 lb dry weight camper, have returned the suspension to stock, and still engage one end of the overload spring with the camper on.
The folks who bought my camper have a Ford F30 with 10500 pound GVWR and ended up with a custom spring pack to achieve satisfaction.