The worst thing with the 350 engine was the thin wall heads. They started cracking around 50/60K miles and joined millions of their buddies stacked out behind automotive machine shops. Easy fix, tho, I used some earlier 882 (thick wall) heads and they ran until the valves and guides got tired. Cheaply rebuilt them. (Several times)
Rear axle 8.5in ring & pinion finally started to howl at around 300,000 miles even tho I was using synthetic lube. Shouldn't blame it because the car towed a lot. By this time, it wasn't what you'd really call a "Chick Magnet".
The worst interior item was the daggummed fuzzy headliner. Good for a couple of years and then the cheap foam behind the cloth would deterioate letting the cloth fall down. I've gotten pretty good at scraping and gluing in new headliners.
Since I can cheaply rebuild just about every system in the car, I still drive it around. Call it my old "Rat Wagon" It'll eventually devolve into a parts car since I recently picked up a really nice '79 Caprice Wagon. I'll fix up the Caprice, toughen up the drive line (coolers, shift kit, heavy U joints, etc, metallic brake pads. Already got a class 3 hitch mounted.
The 79's life with me is just beginning. I'm seriously considering buying a good "takeout" 5.3 litre from a wrecked late Chevy or GMC pickup or Suburban and sticking it in with a custom wiring harness along with an overdrive tranny. This will give much better mileage and power than the old 350.