I been reacing NSS since it started, in 1989, I ran the first race in St. Louis and sat at the table when the rules were written. The first NSS group was actually a match racing orginization. The index racing came later when the group started going to Good Guys, NMCA, and similar events. The orginal idea was to keep the class the way super stock was in the days before prostock, orginally it was 1966 and older full body cars, with dual fours, and stock frame rails. NMCA opened up the class to several body styles to gain car count. And Mopar I guess has the most cost effective combination, so they are the most numerous at all the events I attend. Lot of good racers in NSS, even seeing some younger guys get into the class. Everybody gets along and it is great fun.

https://en.wikipedia.org/wiki/Nostalgia_Super_Stock