I think you have to crunch the numbers regarding the trailer (GVWR) and whether or not towing that amount of weight will exceed any of the vehicle ratings. Also important (and a reason to have more truck then you think you're going to need) is where you will be towing. If you're retiring (we're on a 24 month plan) and planning to travel out west in high elevation areas you're going to want a truck that can pull the trailer easily in the flat lands and handled the higher elevations, meaning a healthy margin between the weight of the trailer and the maximum weights the truck can handle.
We ended up with a trailer with a GVWR of 8.800 lbs and a truck with a 12,500 maximum tow rating and 4,000 payload since our plan is to do some travel out west and realize the power at sea level is going to be reduced significantly at 10,000 feet.
Crunch the numbers and leave yourself a healthy fudge factor with respect to the truck.