86 pickup sitting outside for 30+ years. Where to start?

I haven't looked too close at the wheels but when I do, I'll see if theres any identifying info on them. They are ugly at first, but definitely give 80s vibes.

Not sure what that rattling was, i did have a few tools scattered in the engine bay. On second thought, I think I remember it coming from the grill.

Yeah, first thing I did was see if the engine was seized. I was able to turn the engine manually and changed engine oil and coolant prior to start.

I didn't notice anything unusual with the exhaust besides my muffler falling off during the short drive. Shifts just fine through all 5 gears (minus having to hold the shifter in place in 5th gear because the shifter hits the body).

I topped off the rear diff when I noticed it was leaking before I moved it but I'll try to snap some pictures when I crack that open. Can't imagine it looks great.