I towed the same TT for over 12 years with a 97 F150 and I was over it's GVWR and it's rear GAWR the whole time and it had 255,000 miles on it when I traded... The only reason I traded was because I could afford a new truck after owning the 97 for over 12 years and it was just time.. \
I do wish I could have kept that 97, as it was a great truck and never had any issues.. Never left me on the side of the road.. Well, it did when the alternator went out on it around 2002.. And that was after I jump started a car with my engine running... Lesson learned.. Don't jump start a dead battery vehicle with YOUR engine running.. ;)
It'll kill your alternator big time!
Anyway, look real close to see if you have a full float axle rear end on your 3/4 ton rig... I've seen some that do have 8 lug axles, but don't have the full float bearings...
Mitch