As a Cali resident, my advice is to move, bring it with you and say nothing to the state. This is still legal to do and is the easiest way to address the issue.
Cali legal actually has to do with the firing mechanism mostly. It has nothing to do with the ability to accept magazines. My Cali legal USP was the same USP that could be purchased in all 50 states. My Cali legal Kimber Compact II is the same exact Compact II that you can buy in all 50 states.