Hi,
Mike, when I was looking for a .22 conversion kit for my CZ-75B 9mm, I asked around about the legality of a "conversion." I got the same answer from everyone I talked to except one fellow: it's a "part" and you can put it on, no worries. The one dissenting vote came from a guy in a gun shop in GA, who did nothing to convince me being smart in his State is legal (fortunately I've known enough smart folks from the Peach State to realize he was an anomaly): he felt it more important to lecture me about how screwed up CA is than to take my $300, put the kit he had in stock in a box and ship it to me. Shortly later a fellow in AZ told me there was only one requirement for him to ship one to CA: I had to pay for it first!
Mr. Fifer in his infinite wisdom seems to have followed the lead of that fellow in GA, and would rather "teach us a lesson" here than take our money. In doing so, he took all but one of Ruger's semi-autos off the CA approved list (per Ruger's website--the DOJ link below still shows three until January.) I believe his beef was with the microstamping rule, but apparently he has a reading comprehension problem: those models already ON the list were grandfathered as long as the mfr. renews the approval (read: "Pays the mordida." SOP for CA--everything's about the money.)
If you've already got the LC380CA, perhaps the conversion kit's an option for you as a workaround. For myself, if I wanted a small 9mm, I'd look at one of the mfrs who took the lead of the fellow from AZ and is willing to keep taking our money! Open and above board, not trying to wiggle in thru the back door. There are plenty of them, and several offer a similar sized gun that's at least as good as, if not arguably better than, the Ruger.
http://certguns.doj.ca.gov/ allows you to search for them in any of several ways.
Good luck in your decision!
Rick C