if you read the text above the chart it states "California, the birthplace of hot rodding, has 2,775,004 registered automobiles from model years 1871 through 1972. This represents 5.99% of the total number of registered vehicles in the state" which sounds a little more realistic
i think that the 43% was a typo
as far as hot rodding in cali it depends on what county you live in, where i live you only smog at change of ownership and then not if it is transfered between family, however most areas are bianual