Ok, 86 actually has a few 1 year only parts that are actually good.
on 87-91 SEFI panthers, there's a stupid plastic grommet on the end of the TV cable where it attaches to the throttle body, over time it disintegrates and the cable falls out. When this happens, the line pressure drops to zero and you'll burn up the direct clutch pack very quickly. The fix is to buy the newer copper style.
86 was the first year of SEFI, and they used a 1 year only rod instead, and if it were to fail, the trans actually defaults to full line pressure instead. the 86 setup never seems to go bad though. Pointless trivia.
If it's all original the stock cork valve covers gaskets have probably gone to shit. Get the felpro perma drys if you replace them. Expensive, but they are rubber, reusable, and never go bad.
Same thing with the lower intake gasket, the front and back seals are cork and over time will leak.
If you tune it up, run copper motorcraft plugs. They like these the best. A good quality dist. cap with brass terminals and good quality plug wires.
Do the PCV trio. The PCV valve, grommet and screen. Back of the engine in the lower intake, you have to kinda lay on the upper intake to get to it. There's an internal mesh screen in there which over time clogs up and causes the crankcase pressure to get higher than normal. A long wood screw or lag bolt and some pliers will pop it out.
Make sure the vacuum line to the MAP isn't squishy or cracked. At this point all the vacuum lines could probably use replacing.
Pretty much just your typical 30 year old car stuff.
On the interior, spray the rear panels in the back with some 303, they love to dry out and get all nasty. Same thing with the dash pad.
Box panthers are pretty simple. Nice reliable SBF, the AOD gets some hate but if you take care of it it's fine, nice 8.8 out back. They are easy to work on and parts are dirt cheap.
What are your plans for it?
>my winter beater wagon