Hello all,
I would definitely go with magnetic ones, they are available from pegasus racing supply,
http://www.pegasusautoracing.com/ you can check out the ones I just had made for my
MCS which I autoross with the SCCA. You can buy the magnetic circles, in just about any size you want, and then apply the numbers yourself (you can of course order any number you want), as long as it's not my lucky number.
Don't just stick numbers on your doors, you will regret it for many reasons (some of which have already been mentioned above like paint fade, police, wear, police and police!).
Good luck,
Nick
http://www.mini2.com/gallery/persona...ery_16570.html 
