I've been towing stuff with my 95 F150 with 300 I-6 since it was new. 300 will pull about as well as a 302, if not better. 302 is a fine Mustang motor, but outside it's design purpose in a 4800# truck pulling a trailer. You won't win any races with either motor in a towing situation 351W is a great towing motor IMO.
But brakes really not up to it, as I-6 trucks usually came with the smallest brakes. Long wheelbase definitely better than a shortbed for towing. If you've never had a trailer "wag" the tow vehicle, trust me it's not any fun. 3/4 ton is a better answer for a tow vehicle. I'll second the advice on Broncos. Sold mine last month. Not a good tow vehicle due to height and wheelbase. I've seen some nasty crash PICs from people trying to pull too much with a Bronco. With any short wheelbase, it'll do OK, and then when you aren't expecting it ............ death wobble, and you're pinching the steering wheel in half!