Interesting... that's the first I've heard of the NMCA Autocross series... perhaps only WEST? I'm glad to see it happening!
CAM is mostly unrestricted... 3000 pounds minimum, supposed to be licensed/registered and insured (maybe that has changed).
SCCA Street Prepared (E/SP was once the super-hot pony car class in the mid 80s-90s-early 2000 years) requires original suspension mounting points and has various other limitations within its class rules... sadly, that class is declining in popularity... but the CAM class is exploding. I'm in-between those two classes (CAM and E/SP)... but also campaigning with another club -- MCSCC (hi-speed solo road course events) that has another set of rules and classes here in the mid-west states. See www.mcscc.org
for viewing their hi-speed autocross rules/classes, etc... very active with W2W racing, as well.