Reverse your game plan....get the new 3/4 ton truck first, and then buy the trailer. Otherwise, you'll end up buying a trailer that will be too small (or weigh too much for your current truck) and you'll be unhappy with it. Once you have the truck, you can buy a trailer that has the room you want and can be safely towed. Personally, I like the guideline that you are better off towing 80% or less of the maximum capacity of the tow vehicle. But...it's still important to crunch the numbers and know you haven't exceeded payload.