I think the OEM option are just modern shocks of the correct length. Nothing to do with 1979 "original".
Also likely is that OEM (AC Delco) means a farmed out part with blue paint and a sticker.

Yes, after thinking more about this I think you are spot on. And considering that, there's no way to tell how they would behave until after they were installed. I'm changing my answer, and I would go with KYBs hands down.

I had a feeling GM just outsourced their stuff and put their name on the part nowadays. True OEM suspension parts for these cars were made in the Delco plant in Kettering, Ohio, a half mile down the road from my parents. That got cut and Tenneco bought up the property. Now they're leaving as well. Haha. Brake components were made in the Moraine Delco facility, which is now a huge field, soon to he replaced by a Love's travel stop and hotel. I always assumed those jobs were moved to some new facility in Mexico or China that made AC Delco, not that they legitimately paid the lowest bidder to supply stuff. I give them too much credit. Haha.

Everybody does it, and it's not necessarily a bad thing. It costs too much money to have your fingers in too many pies, and . Why divide your focus by making 100 different things, when you can just buy your shocks from a company who specializes in making shocks, your brake pads from a company that makes brake pads, tires from a tire company, etc. It makes logical sense to me.

In my mind, it exposes your business to much less trouble if you supply your own critical parts vs relying on someone else. The chip shortage is the classic example. Tires, mirrors, light bulbs, etc. Are places you can get outside suppliers, but mechanical parts I would do in-house. Your final quality in that is only as good as your weakest supplier. It also pretty much destroyed the industrial core of our city. The old timers around here referred to Dayton as Little Detroit because of the all of the car manufacturing. Haha. We are in a little better shape than Detroit nowadays. We had a massive Chrysler plant, that's now Mahle, I believe there was a Ford plant in Vandalia and several GM plants. Several area suppliers worked with them as well.

Trying to make everything, and do it well doesn't always work. This is known as "vertical integration". There are benefits and losses (see wiki).
.
Chips are an extraordinary case. There are very few chips fabs in the world because it costs billions (trillions?) of dollars to set them up and run them, and years to train specialists to work there . Its a cutthroat industry that exposes you to tremendous financial risk. As if cars weren't risky enough. Only massive corps can make chips. There's no way that car companies can make chips. I won't even get into the convoluted mess that is intellectual property.
.
On the other hand , you see companies like Apple. They ditched Intel, and brought their chip design in-house (design, not manufacturing, mind you), so that they would have more control. Intel was abusing their relationship and hindered innovation. But only a big company like Apple can do that.
.
> In my mind, it exposes your business to much less trouble if you supply your own critical parts
Managing 100 different supply chains is not easier than managing 20.
If you get into the business of manufacturing starter motors lets say... well now you have to set up suppliers for copper, and silicon steel, and graphite, and so on and so forth. It's easier to outsource all that headache to somebody else. Good inventory management is pretty important, but in a crisis all bets are off. When the issue is raw material, then everybody suffers.
.
> Your final quality in that is only as good as your weakest supplier
If vendors aren't meeting quality or quota targets, then change vendors.
.
>It also pretty much destroyed the industrial core of our city.
That time is gone. It's never coming back. Globalization changed the world. Americans don't want to learn practical skills or get their hands dirty any more. Adapt or perish.