I'll tell you a funny story about my old '84 GSL-SE. The previous owners of that car were very close friends of mine -- almost like second parents to me. The husband was anal retentive about auto maintenance, and the wife was the primary driver and didn't think much about what goes on under the hood. It was her car, and his toy. Nothing unusual there.
One day, while driving from their beach house at the Jersey shore back to their regular home at the New York state line -- about a 100 mile hike -- the oil-level warning light came on. She kept driving until she got to the next service area, where the pump jockey eventually identified that the oil drain plug was missing. (What this says about her husband's normally impeccable auto maintenance skills, I'll refrain from judging.) Regardless, she had to get home.
In an incredible demonstration of her natural-blonde mechanical aptitude, she chose to put a quart of oil into the car, and drove to the next service station, where she repeated the same routine. She hopped from service station to service station for the next 30 or 40 miles, at highway speeds, without incident. When she got home, she parked the car in the garage, and told hubby about the whole ordeal. They lived at the other end of the street from me, but I could swear that I heard an anguished male voice cry out in astonishment that day.
Anyway, he installed another drain plug, refilled the oil, and they drove the car another 10 or 20k miles before they sold it to me. I put on another 50k miles before that engine coughed up an apex seal between turns three and four at Summit Point raceway, at 137,000 miles. So I'm going to guess that MAYBE this one incident took between 20-60k miles off of the life of a potentially 200k mile engine. Or maybe not.
What this really tells me is that these 1st gen engines have incredible durability and resilience and that, in all likelihood, if you ever run one of these engines while low on oil for any brief period, that you will probably never notice any problems resulting from it. Rest easy, rev freely, and don't worry about it.