Yes, Stuart,
And when we recreated the Clinchfield version it was with a bolt on sign (For the tender) but I can't remember what we used for the cab sides (this was over 15 years ago mind you). We had the permission of CSX President Jerry Davis to bring the 3985 to West Virginia and the assistance of a number of individuals who styled themselves as the "Clinchfield Conspiracy" who supplied us with information and even the proper number plate.
The first time that I remember using stick on magnetic lettering was on the Rocky Club anniversary trip where we changed the number of the 3985 to the 3745 (I think, I'd have to check the photos) to commemorate their trip behind the 3744 on one of their earliest excursions on the UP. We even had a new number plate cast for it. I made the magnetic lettering in the Roundhouse there in Cheyenne and it was actually spray painted on the background. If I were to do it today I would use laser cut Vinyl lettering on a black background, but lasers were not available to us back then.
Before you get excited about recreating a D&RGW 3800, let the Steam Crew and UP 3985 get the drivers back under her, get the locomotive into tram, and the new pins and brasses used to each other.
Rick Steele