Todd,
I've placed them on the door and the front fender depending on size. You can get a bigger # on the fender and when I switched from my 2 digit football number to the 3 digit (004) serial # of my ERA, I went the front fender route. If you sift through my gallery you can see both placements.
http://cobra.terraworld.net/photopos...at=500&thumb=1
Cheers, Pete C