When I bought my truck, the diesels on the lot were well over 1000# heavier. You have to go up to a 350 to have the same cargo capacity of a gas 250. Diesels have much less payload. No single piece of your cargo, except the camper, weighs as much as the diesel, and it's extra batteries, extra alternator, extra........
I have 3100# cargo capacity. Any pop up camper will be well under that. Watch your option packages as well. Options have weight. F250 rear springs are a bit softer than 350. I hope to avoid the cost of Deavers.
Gas f250 xl fx4 ccsb with a fwc hawk camper is hard to beat, and within your budget. 40k for truck, 25+ for camper.