You want to consider Braking Power. Hauling weight demands a lot of stopping power. Flat land you might get away with a 200 Gallon tank if you drive careful IMHO. Hill country go with no more than 150 gallons.
F150 are only sedans with a bed on the back. What you need is a real truck which start at 3/4 ton rating. GVW is calculated by the Braking power.
it is one thing to do a off label applications. It is total stupidity to post it on the world wide web and expect people to approve.
You can lead a Donkey to water but you can't make the Jackass Drink