Yeah and Texas currently does that except:

A. Classic car status should only apply to cars 25 years or older with original equipment only. Mileage driven should be limited.

B. Hobby car status should only be given to a certain number of cars. Mileage driven should be limited.

I don't think the guy with a hopped up Camaro or Mustang should be able to claim exemption from emmisions statutes just because the frame he built his car on is so old. That is why so many people are buying old Ford and Chevy "classics". They don't have to worry about emmissions when they tune them since a cat (or anything for that matter) was never standard equipment.