I try to keep my 66 coupe as stock/original as possible. I'm not really upgrading or modifying it. A removable rear window demister and a super stereo are the only additions, but I wouldn't call that modifying....
The PO however did change the color of the exterior by simply respraying it white without stripping a thing. I soon discovered it's true color, Prairie Bronze Metallic, which is not a color I can live with. Though I saw some pics of stangs in that color later and it doesn't look as bad as expected. It actually can look good, just a bit dull...
So in conclusion I am keeping the new ext. color (white) in my bare metal respray. To match that, I have put in a medium blue interior, which was parchment/palomino originally.
Depending on how you look at original or stock as a definition, my car is not original. It didn't leave the factory this way, but I'm using standard colors which were available then, so if you look at it a different way you might still call it stock.
Just depends on your view.
Columbo
First time rolling restoration, 66 289 nearing completion.