Dave
Just a note and I am sure you are aware of it, but be very steady flating the wheels off, you do not want to destroy the chromate finish to the wheels.
I would suggest having this redone, as I know your front wheel has a little corrosion. You may get away with using a di chromate primer if the area is not too large.
The guy that used to run Dymag offers this service - Steve Turner, TPCS
http://tpcs-magnesium-refurbs.co.uk/ not used the guy personally but know of many that have and say he's great.
Also when having them repainted ensure the finish is semi matt / soft sheen..........you can tell I am not a painter !

if your looking for a truly original finish.
Take that number to any paint mixers and they know what you want
Clinty