Easy way to determine how much Travel Trailer I can buy?

Weigh the truck loaded ready to travel. Add 100 pounds for hitch. Look up the trucks GCWR from GM. Subtract B from A. That is the max towing capacity per GM compliance engineers certified to the feds. If you adhere to the 80% rule then 80% of the left over weight number is the GVWR of a trailer you should be looking for.