The issue with the bronco is the wheelbase. It's a very stout vehicle and with the 351 would probably be able to do it. Will it last long doing it? Probably not and you'd probably end up with worse mileage than the F250. The Ranger isn't even in towing ball park as mentioned earlier. I'd say run 33's on the F250. Regear to 4.10 or even 4.56 if it sees more trail than highway, and then hop up the 460. It's very restricted in the intake and exhaust from the factory and there are plenty of other things you can do to it. It might get you into the teens mileage wise but still be able to do everything it does now. If you're worried about the body being too nice you need to save up and get a trail toy, otherwise bob the bed to the rear leaf spring hangers, boatside the cab and get some steel bumpers front and rear and have an awesome all around rig that can run trails without major damage and still be a dd/tow pig.
1993 Ford Explorer- Factory 3.73s and limited slip, 31x10.5 General Grabber AT2 on 15*7 ATX Slot
2002 Expedition 4wd- 5.4L, 285/75/16 Falken Wildpeak AT, factory limited slip
2000 F-150 2wd 4.2L, 5.5" front 3" rear lift, Bilstein 5100s all around, 33" General Grabber AT2, 130w KC Daylighters, Dual 4' Firestiks
1997 F-150 2wd 5.4L, coil spacers 265/75/16 BFG AT's
1968 Camaro convertible, 350,th350, white top, Corvette red with white racing stripes(still have).