Would it be possible to preserve the old lettering by spraying clear coat over it, and designing some type of decorative border around it? Once it's preserved that way, repaint the rest of the sheet metal around it. A good sign man can freehand some sort of decorative border around the original logo to blend in with the new paint. Just an oddball suggestion!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!