I sent an email to the DOJ firearms division asking about the legality of ordering replacement mag bodies (well, see my exact wording below)  Here is the response:
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Dear Mr. XXXXXXXXX:

   This is in reply to your e-mail  of 08/01/03.  Replacing parts on a high capacity magazine is not specifically addressed in Penal Code 12020.   You need to check with your local law enforcement agency and/or city attorney's office for their interpretation of the law.  These agencies would determine if your actions conflicted with the law and if prosecution would result.  There are 58 counties in California with 58 district attorneys, all of whom are officers of the court.  Add to that all the city attorneys of incorporated cities who are officers of the court and you can see that there might be varying degrees of interpretation on what would be breaking the law.

    I am not a lawyer and cannot give legal advice.  I do not see any conflict with the law with acquisition of hi-cap mag parts for replacement and/or repair of your personally owned magazines.  But the best information I can give you is to seek your answers at the local level.

Sally S. Carney, Field Representative
Firearms Division


>>> <XXXXXXXXXXXXXXX.net> 08/01/03 02:48PM >>>
Below is the result of your feedback form.  It was submitted by
(XXXXXXXXXXXXXXX.net) on Friday, August 01, 2003 at 15:48:28
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Name: XXX XXXXXXXXX

Telephone: 707-XXX-XXXX

feedback: I am a California resident.  Can you tell me, is is legal for a firearms vendor from another state to sell to a California resident, replacement parts for EXISTING, legal, high capacity magazines?  (such as springs, floorplates, followers, bodies).

THANKS!
--Dan

So each jurisdiction interprets the state law different? Damn  what a crock-wonder if ever has a given a straight answer?

Official translation: Since 58 county attorneys have an individual interpretaion of the law, then since there are currently, as of Jan, 2003, 35,591,000  [subjects] in the Republik of Rough and Ready, each must surely have an interpretation as well.

That which is is not prohibited, is permissible.