I have never pulled a 5th wheel with a Gasser. However I received some advice that has served me well. First, pull a 5er with a diesel that way you won't have to buy two trucks. Second, If you have to worry about the price of fuel you can't afford to RV.
Now the last one is not meant to be rude, however it is correct. If your buying a 5er to just camp on weekends then you can take trips when you can save enough cash for fuel by planning. If you plan to go fulltime or part time then you stay in one spot until you have the cash for fuel.
If the Diesel fuel goes up to $5 a gallon I will not be happy, but I will keep fulltiming. I will just have to set a bit longer.
Now one advantage for you. The price of Diesel fuel is outrageous. It is most likely that there will be some good Diesel's on the market at a low price. When I purchased my F250 the price of a used Diesel was very close to the price of a new one so it made good sense to purchase a new one. If you take your time you should get a good buy on a Diesel.
For the 5er's you indicated most 3/4 ton Diesels will handle the 5ers. And if I were you I would look at those with a full size bed, then you can use any hitch you like. I like the B&W. It is a little expensive but at my age I need to be able to lift it out easily and it allows a clean bed when removed..
If your going to go fulltime or think you might go fulltime I would really look into a 5er that has plenty of room, 4 seasons, and would be comfortable for your family to live in. That is why I traded in my 30ft, 2slide, queen bed 5er for a Bighorn 3400RE. The Bighorn is much more comfortable to live in fulltime. Look to the future as what your going to want to do, take your time and get the one that will meet your needs. Then you only have to pay for one rather than two or more. I speak from experience.
FWIW
BC