Racer,
Here's the scoop. All vehicles that are 1973 and older are exempt from testing, but not from having the original equipment.
If you plan to do a "legal" conversion, you are supposed to tell the DMV, who will then send you to a referee station for a 1 time check that you have all the required equipment. That applies to an exempt vehicle (73 and older).
Bang is correct. In 2003, the rolling average is to take effect which will make 74s exempt and in 2004, 75s exempt and so on. However, CARB has a proposed "Clean Air Plan (CAP)" which will attempt to get rid of the 30 year rolling exemption.
If you look back in the "Misc. Tech" section, there are a couple of posts that I started with links to the CA vehicle code and the CAP. MAybe try doing a search on my member number in this section.
Tim
Here, I did the work for you:
try this one
or this one