Ernie,
I understand NASCAR history to be as you describe it also. I never heard of a restrictor plate until 1987 after Allison (I think) went through the fence at 210mph at Talladaga and almost wiped out a bunch of spectators. I found the suggestion that Petty's (Chrysler's) success was a result of Ford's being "handcuffed" by the restrictor plate...well...interesting.
Scott