I talked to the two guys driving the 510's...they were even older than me!
They said they survived this long since they're so serious about their roll cages...these two Datsuns had about the most substantial roll cages there that day; similar to what you'd see in a recent NASCAR stock car.
I always loved 510's too, remembering them from back in the early to mid 1970's and the days of TransAm when John Morton, Bob Sharp and others were so competitive with them. I saw them run quite a few times at Watkins Glen, NY.
Since I don't want to convert my Supra into a hardcore racecar, I'm looking into building and club & vintage racing something and a 510 is a damn good candidate.