As far as the feds go there should be no problem as it is over 25 years old. If in pieces it may be easier to get someone with an import license to bring it in as used parts. I would try a caterham dealer for that. Getting it registered may be a problem in CA so I would probably title it in an easier state and transfer from there. I am in WA and have titled several vehicles with no bill of sale or title. All it takes here is letting the state police inspect to make sure it has a VIN or serial number on the frame and then buying a registration. The only draw back is they don't give you a title for 3 years. I've done this with garage finds and mecum sales, no hassle. Check around,other states may be easier. If you try WA I can help.