(I'm a noob here at MLU, so for all I know you've all seen this website....)
The Armoured Acorn (
http://www.armouredacorn.com/) is the place to check before you apply tac/unit markings to your vehicle.
I had a couple of questions concerning the WW2 markings on a CMP ('coz if they were original I sure as shooting wasn't going to grind them off!) and Barry quickly and courteously* replied to my email.
* Hey, he's 'Armour' and I was 'Infantry' and that feud's been going on a while now)