I've got a 97 Exploder with a 302 and almost 200k on it. I love that truck. The transmissions seem to have issues for some people, but most chattery shifts and such can be cured or greatly improved with synthetic fluid and a new filter on a regular basis. It's a 4R70W trans in the V8 models, and it's a pretty robust piece. If you get one in good shape, look up the J-mod as an easy modification that will keep it in good shape.
Mine has the factory tow package and is rated to tow 6750 lbs or so. We tow a 2500# popup camper all over the north GA mountains with no problem. It actually is better towing our popup than my buddy's 2005 F150. I'm pretty sure with a brake controller and a WD hitch I could tow my Mustang on a decent trailer if I needed to.
Mileage is....not bad, actually. On a flat, interstate run to Florida TOWING THE CAMPER with the OVERDRIVE OFF I still get 16mpg. Interstate, no trailer, cruise on, I get around 18. Around town, it's no worse than my 05 Mustang, and easily better than most pickups. I have seen a guy on the internet getting almost 30mpg from a 2wd 302 with a LOT of minor tweaks and careful driving. But it's not realistic for any other driver.
Parts are cheap. Like, the cheapest vehicle I've ever looked up on Rock Auto. Parts vehicles are readily available nearly free.
Points of interest: interior pieces in good shape are getting scarce due to age. On the 302 there's a metal downtube from the EGR to the exhaust manifold that likes to develop a hole. At idle and under load, it can be mistaken for a tap in the motor, but is easy to fix. Cruise Control buttons are all melting from age but replacements are available for about $100. Avoid the leather interiors at this age, out cloth XLT interior still looks great. Beyond that, normal wear and care issues apply.
For more info than you ever wanted, hit ExplorerForum.com. They have more posts in a day than we have members. And some of the 4x4 built trucks over there are insane. Signal-noise ratio is a little high, but there's a ton of info if you search for it.
Can you tell I'm a big fan? Our truck has been the most reliable, ready vehicle I've ever owned. In 07 we contemplated replacing it, but there was nothing on the new market that could do everything it can as well as it still can.