Issues
I bought a 86 L98 manual shift convertible a few months back and I have run into a few items.
Clutch master and slave were replaced because the slave went out. It's a bear to bleed (I've added info on what worked for me in another thread).
The interior light delay is bad, found a used on but haven't put it in yet.
Dash light bulbs (2 of 4) were out. Use 882 bi-pin if your has the long pins on the bulbs. I have found some bi-pin leds on EBay that are supposed to be direct replacements I'm hoping to put in this winter.
Check the vacume hoses under the hood. I've found a couple so far broken off due to age.
Watch if you keep the hood up a while, it drains the battery fairly easily. I found a plugin switch setup at Ecklers (I think) that adds a on-off switch so you can turn them off without pulling fuses, connectors or the battery.
Battery tender or unhook the battery if not driven for some time.
I am also planning on replacing the swaybar bushings and brake pads over winter.
I also have an issue with the parking brake switch, comes on at times. Push it down and the light goes off - need to adjust that.
I also have a squeek in the drivers side rear wheel I'm going to have to look for. Only happens on accelerating from a stop, otherwise quiet.
The elbow that goes from the egr pipe to the plenum was replace with a piece of heater hose and it was junk. I found a piece at NAPA that was a 1/2" with an elbow in it. I cut it down and it works fine.
Last one is the 'anti loc' light comes and goes off at times. No idea yet on that one.
You'll find a number of parts are no longer available so used or rebuilt are your only recourse. If you see something you might need, get it while you can or you may not find when you need it.
That's my list. Hope that helps.