Brakes were mentioned, but specifically, look at the rear wheel cylinders. Pull the dust cover off a bit and see if any brake fluid comes out. Have seen many with slight seeps, that turned into leaks.
If you look under the rubber seal for the back hatch (carefully) you might find where the seam, where rubber mounts is rusted through (usually around a spot weld)/(near the bend at the bottom), water runs down the outside of the rubber seal through the rust hole into the rear carge area.
The rain gutters on the roof, occasioanally leak (small cracks in the mastic and paint), especially at the ends. Water will run down through the pillars. Super glue or winshield sealer has worked for me.
Distributor caps seemed to wear out quick.
Might have a look at the starter brushes, fairly easy to check.
Same with the alternator brushes, not so easy to check.
Loose idler pulleys (bearings) , on the alternator belt.
I always check every connector I can find for moisture and/or corrosion. Do a visual on the pins bent/ slide into the connector.
Vacume lines, crack, rot and chaff, worth a carefull look.
Check and see if your tranny cooler lines are rubbing on the steering box, ditto with the power steering return line. Check the connectors for the tranny lines under the radiator for leaks.
I´ve been poking around mine for six months, find something new every week.
Like mentioned before, grounds, pull and clean all, add star washers if necessary, biggest driveability improvement on mine was doing the grounds.
Like mentioned before the wiring under the drivers side carpet is worth a look.