How badly will I hurt the value of car?
 

The car in question is a 1964 356 coupe. It was originally red with a black vinyl interior. Although the car is fairly sound it is in for a complete restoration. I would love to see it a metallic silver with beige interior. A 64 non sunroof coupe restored is not the high ticket item out there but how much do you think I'd hurt the value changing the color and interior?

Not a lot, unless you are trying for a concours type car.

You won't lose value if it's done well.

Kevin-
(Quite) a few years back, I sold a '64SC non sunroof coupe for far above market value, after changing the color to Bahama Yellow/black.
The buyer liked the color change/quality and had to have it.
After seeing your work "on cam", I know you'll do the silver car right, and will also put it "above market".

I agree. I've only owned one 356, so I'm not an expert. But, a well done job is always welcome. Can't hurt, IMHO.

I spent a lot of time at the recent GAF. Everybody seemed to have thier COA's on display. I don't think the owner of this one will likely be competing for any awards where authenticity is a factor. I really liked the silver cars over the reds so I'm still very tempted. I tend to agree that an excellently exacuted finish is valued more than originality.
If I can't decide by the time it's ready for the spray booth I'll just make the car owner decide (just kidding).