The installation, prior to January 1, 1974, of an auxiliary gasoline fuel tank for use on a 1973 or earlier model year motor vehicle, which vehicle is required, pursuant to Part 5 (commencing with Section 43000) of Division 26 of the Health and Safety Code or the National Emission Standards Act ( 42 U.S.C., Secs. 1857f-1 to 1857f-7, inclusive), to be equipped with a fuel system evaporative loss control device, shall not be deemed a violation of Section 27156 of this code. As used in this section, the term "auxiliary gasoline fuel tank," has the same meaning as defined in subdivision (b) of Section 43834 of the Health and Safety Code.
Ca. Veh. Code § 27156.1