With a somewhat more macro view of the OP's querrie, I would say keep your ear to the ground and spread your net wide to find the best deal on any 1, 2, or 3 series truck (that's Ford, GM, and RAM) that will carry your camper without upgrades and without being too close to the edge of GVW. This includes finding a good deal on slightly used trucks. A 2 or 3 year old pickup has lost some value. If looking at used, take a sage guru with you that can tell you what you have and even do some negotiating on the price if it comes to it. Time and travel may come into the picture.
The other issue: Gas v. Diesel is a matter of how long you plan to drive said rig. If less than 150K miles, a gasser should do the trick. If in it for the long haul, say 300-400K miles, an oil burner will finally pay off the $12K 'diesel penalty'.
California is trying to rid itself of all those polluting diesel pickup trucks by slapping on a huge increase in the cost of diesel fuel, now the highest in the country. I heard one politician say that if you want to leave California with your diesel pickup, feel free, as we need the space for a lot of immigrants that can replace you.
jefe