A few checks before college

Timing chain slop can be easily checked without removing the front cover. Turn the engine over by hand while watching the distributor rotor. Then reverse and see how far before the rotor follows. Of course, use the degree mark on the crank damper to measure. Anything over 10 deg is cause for worry, though it could probably run for another 100K fine. Slop also makes the timing light mark jump around.

Wheel bearings would be #1 since that can disable you (did me). Suspension and steering slop won't usually stop you, nor the U-joints. I found a totally rusted out U-joint in my Dart and found that was what made the clunk when I shifted from P to R the last 100K miles. Got so bad I felt a vibration ~55 mph, but still drove 400 miles home.

Of course, electrical is the main disabler. Carry spare ignition parts (points, ECU, ballast, ...), alligator jumper wires, a wiring diagram, multimeter. I have a Battery Brain in all my cars, plus wired mine so I get a buzzer if the headlights are on with ignition off. Mini-starters are so light you could carry one in the trunk. I even carry a small carb and electric fuel pump in case my fancy EFI dies. When I change hoses and belts, I keep the old ones in the trunk under the spare tire. This is in all my cars, and they have come in useful. In my 96, I carry a complete timing belt kit since I waited a week for parts once. Similarly, in my 02 I have a spare p.s. pump plastic pulley since getting one wasted a whole day once. New cars will disable you quicker. If anything on the serpentine belt fails, you are down. Parts for new cars can be harder to get than my old Mopars, in my experience, and can cost $$$.