DISCLAIMER: I like diesels better than gas engines for heavier hauling, towing and long drives. I am a diesel and big torque fanboy. This post is intended only as an add'l point of view for the original poster.
The three arguments for gas engines you will hear usually go: 1) gas engines cost less to buy and operate than diesel engines and make adequate power; 2) gas engines are lighter than diesel engines and therefore diminish payload less; 3) diesel engines will experience costly breakdowns because modern diesel emissions systems are complex and unreliable.
I would not even consider the purchase of a gas engine powered rig for hauling a truck camper plus towing, but a gas engine will do the job just fine and I can understand why people might prefer them to diesel engines. As for #1 above, diesel engines in 3/4 and 1 ton trucks are way more powerful than their gas engine counterparts. (A 2015 Ram Cummins 2500 (non high output) makes 800 lb/ft of torque. The diesel engine option is, however, much more expensive than gas, averaging about $9000 as an engine option at purchase. On the other hand, quite a bit of that upcharge comes back in resale, and the purchase delta is less in the Ford variant if the comparison is a 6.7 Powerstroke to a 7.3 Godzilla gasser (If I recall correctly, the Godzilla V-8 is about $2000 as an option). I don't bother with "break even" analyses factoring in estimates about fuel economy and future gas prices. It's all guesswork. Diesels probably do cost a bit more to own and operate. It is, however, a fact that diesels resell for more than their gas engine counterparts.
As for #2, that is completely true and it is an important point! By way of example, in a RAM platform, the Cummins 6.7 diesel is a nearly $9500 option, and will significantly reduce payload because it is very heavy. A 2015 or so RAM 2500 Crew Cab, 4x4, well optioned in Laramie Spec will have payload around 2100-2200 pounds. In your case, four people in the cab, a loaded out FWC Hawk, water, fuel, etc. could easily put you near, at or over max payload for that 2500 diesel truck. The move, then, would be to put your rig on a diet and bring it in under payload max; or consider a 3500 single axle diesel truck as your base platform; or look at a 2500 gas engine platform to save engine weight. (NOTE: the most reliable way to determine exact payload is to read the sticker on the door of the truck you want to buy. After that, I suggest joining truck specific Forums, which frequently have "Post Up Your Payload Sticker" threads. You can read through those to find the exact number for a truck optioned close to what you want.)
As for #3, I flatly disagree with the blanket statements from primarily non-diesel owning people that modern diesels are unreliable due to complex emissions systems. I suggest that you join some diesel forums for the truck brand you like and do your research. I did (plus I have owned one 2500 Cummins Ram + 3 Hemi half ton RAMS, all nearly perfect) and am comfortable in the conclusion that diesel emissions systems, while complex, are nowhere near a disaster guaranteed to happen.
At the end of the day, a gas 2500 or maybe 3500 Crew cab set up like RamblinChet's RAM (see his post above and his build thread for how to do things right...) might be a great rig for you. For me, drop the diesel in there and it's even better.
