Get a used F250 Diesel.
They are work trucks. The deisels will pull 250K miles and 6,000 lbs is easy work. Make sure you make it 5th wheel (gooseneck in Bed). No dualies needed.
We towed a backhoe everyday along with attachments, 2x12 and iron stakes (sometimes 12,000 lbs.) for about 200K miles on that truck before the crankshaft snapped.
You’ll also get decent gas mileage for towing.
(Hint - Keep oil in the crankcase)
(Hint - Keep oil in the crankcase)
I take it we don’t need to ask you how you know.
Thanks. I'll remember that. d;^)