Think about it. A good portion of the 409 Biscayne's, Impalas have been eaten up by the low ride crowd, especially out in the West.
The Fairlane's and Thunderbolts are hard to find in decent shape and are probably still not as competitive. Though the 922 guys might argue that point with some muscle.
I personally would love to see the NSS races have more GM and Ford/Mercury products competing.