Harleyrider, it was over 3 years ago, so I can't even remember what color the car was. I think they started the Bill Board like it was coming out of the side vent.
I was never a big fan of Cuda's with Bill Boards, so that's why I wasn't crazy about it on the Crossfire.
But if that look is something you think you might like, just paint up a model the way you want to do it, and see how it looks.
These cars are selling for so little money new, and their resale is in the dumpster, I'd never worry very much about keeping them original, unless that look is what floats your boat.
Do what ever makes you happy, the only person you have to please is yourself. (Well maybe the Wife every now and then too).