Common problems?
Well, anything thats common on Ford trucks.
First off, Rust, Wheel Arches, Rockers, Cab corners, are the places to really watch. In addition on the bronco the tailgates seem to get eat away as well.
Power rear windows, also seem to take a shit in short order on them.
The removable tops, seem to also leak like a siv in anything but the lightest rain storm.
The 300 inline has a Electronic Feedback Carb that is an absoulte nitemare, its easy to remedy though by changing it out with an older (pre 83) 1bbl from a 300, or going all out and putting a 4bbl on it.
The 302 of that era was EFI, so igntion module problems are common, as are Fuel Pressure regulators and other electonics relatated issues.
The 351's seemed to be pretty solid that year problem wise, the holley carbs on 4bbl versions were known for sticking floats though.
The rest of the drivetrain, the C6 and T18 4sp's are pretty much bulletproof, the 3spW/OD trans (that i forgot to metion eariler) is a decent tranny, but is usually used in conjuction with extremely high rear end gears, and makes for an overall dog of a vehicle in the power Department.
The AOD Automatic Overdrive is a decent trans, just dont abuse it.
The axles are pretty troubless.
Automatic Locking hubs, avoid. Sometimes you get lucky and they work, other times they are junk. They are eaisly replaced with lockouts though.
Im not sure if the Touch Drive 4x4 was available in 86, but if it was, AVOID IT LIKE THE PLAUGE, they are junk (not the transfer case, but all the electonrics assosiated with shifting it), get one with a manual T case.
As far as fixing wheel arch rust, the only right way to do is is cut them out and weld in new panels. Wheel archs rust from the inside out so grinding off surface and repainting it will only mask the problem for a few months at best.
later,
Dustin