That does depend on the tire you are running, the modified tire KK704 or Hoosier G-60 are legal at Napa, I'm not sure about UCS if they still allow them or if they went back to only allowing DOT tires, but those gum-ball sport-mod tires aren't allowed. UCS will stick you with the next higher stockcar class and Napa will just turn a blind eye, just like they did with the cheating drivers running quick steer in their street stocks...