May have answered my own question...
A call to CA DMV reveals any vehicle 25 years old or older is exempt from EPA / 50 state compliance.
If anyone has had a different experience, please advise before I spend any money..!
Ducati 1999 996S - mildly modified
Ducati 1992 851 Strada - bone stock
Ducati 1995 900SS/SP - extensively modified
Ducati 1981 Darmah / Bevel - extensively modified
1967 Bridgestone 350 GTR - a cafe racer in the making