The way I'd like to see it:

All Makes
10.5s only (w's ok)
Multiple Carburetors (no Dominators)
3,000 lbs. min. weight
Obviously N/A
period hoodscoops
Engine style must match year of car.
No pony cars (Mustangs, Camaros, post '68 Cudas/use body styles accepted by majority of NSS groups)
NSS interior rules

Basically accepted NSS rules with min. weight, 10.5's, trans brake/two steps,and a pro tree.

Keep it simple.