Ok, yes I have to admit a few good things came out of Ford, and I agree with your example.
My current square is at 231K on it's 350. Setting aside all synthetic oils for a second, the one additional thing I will say is that standard "dino" conventional oil, got leaps and bounds better in the 80's and 90's. Mainly in their ability prevent deposit build ups, and to leave a film to prevent dry starts. So if we go back in a time machine for second in 1975, it was much more likely for any engine to wear out faster because of the oil that was around in those days. Another thing, anyone remember the awful deposits that Pennzoil use to leave behind, it use to be said it was small amounts of coal in the oil building up over time. I have no idea how true that is but I do know at least into the late 90's / early 2000's area we'd see engines all slugged up because of Pennzoil use. Surprisingly enough a poorly adjusted choke if left badly out of adjustment for to long can take a toll on engine life as well. A pull off not working can cause cylinder wall wash down at every cold start, do that over and over again and it can do a lot of initially unseen damage. A choke to lean might cause the driver to pump the crap out of the gas and then rev it excessively high to keep it running. Lot of variable for sure!
As far as the 4.3 thing is concerned, I worked at one point at a place that had a fleet coming to us with a bunch of Astro vans, and unlike most fleets these guys took care of their rigs. They had many make it to high mileage 200K+, the biggest down fall to the 4.3 IMO was the spider injection. and the flat top distributor caps had issues with the cheaper aftermarket ones but those issues were not exclusive to the 4.3.