Unless you are the original owner, it is going to be hard to tell a factory F up from a PO F up. Even then, with the amount of time that has passed, it may difficult for even an original owner to tell his own F ups from the factory's. The only factory issues I have had with my Regal are design flaws, not assembly issues.
My dad switched to Ford in the early 90's after his 84 Toyota rusted away very quickly. I can't even remember that pickup without rust holes. 70's and 80's Asian imports were rust buckets, even today they still have some rust issues.
Does the air cleaner lid have a raise area around the stud hole? I bought a 78- up era 4 barrel Chevrolet air cleaner and the lid has this raised area. Never seen another like it. I would assume it used a similar washer?
I was always 100% gm when messing with older cars. Once I shifted to something modern, I had no choice but to go with ford for a mustang due to value (hp and options per dollar it'd cost about 12k extra for an equal camaro).
Wife's mustang we got new has 103K miles on it. Haven't done anything except oil changes - no plugs/wires, nothing at all ever except oil and oil filters. Still on the factory tires that are close to the wear indicators, so you know she doesn't burn out.
Ill be sick if anything happens to my 04 Monte Carlo SS, its getting ready to hit 99,000 miles. Crossing my fingers itll keep going well over 200,000 because i just couldnt bring myself to buy much of anything the big 3 makes anymore. In the muscle car world i can say that the looks have gotten really good, but the quality is complete crap. A few guys at work have been eating up overtime and treated themselves to a new Challenger for one and a camaro for the other. Well just a month into it the challenger is gone because it was in the shop so much the guy wasnt able to drive it so he traded it for a truck and the guy with the camaro said it was made so cheap he tossed it and went back to his beater daily driver. Not so promising. Sadly, and i cant believe im saying this, my wifes Fiat has quite literally been the best little car with almost ZERO quality issues. Probably just jinxed her there but for the Italians its quite a surprise