I totally agree with emcvay.
A modern F350 SRW can handle either or those campers, possible with a few modifications. Will you be over the GVWR? Possibly.
I carried an 11' camper on my '07 Chevy 3500 SRW. The whole thing weighed in at 11,140 pounds. The truck's GVWR was 9,900. I drove this rig for thousands of miles thru multiple states. I added heavy duty shocks and air bags. I was not over the tire or axle ratings of the truck. This is perfectly legal despite what some will insist.
However, I strongly recommend getting a dually. When I started carrying this same camper on a dually the difference was immediately apparent. There was significantly less bounce, sway, and rocking. The dually was a much better driving experience. And, it was also over the GVWR; 13,100 on a truck rated for 11,400. Again, I was not over tire or axle ratings.
As for the dealer who will only sell to a diesel owner, he's a complete moron. Take two identical trucks, one gas and one diesel, and the diesel truck will have less payload. I would buy from the other dealer. Then, take your nice new gas F350 and camper by the diesel only dealer and tell him how happy you are that you bought from the other guy and how much you love your gas truck.
