Like 283v8 said, all original has more value.
And like 283v8 said, enjoy it and drive it.
From what I've seen you need to balance what the market "would" want to buy and what "you" want.
If the car is a rare car,like a 65SS or a special ordered/historical/famous 65 Malibu, you would be decreasing its value by changing anything from its original state.
However, if it is plane Jane 2 dr V8 and you are trying to make it more of a "looker" than it is, will depend on what you want.
It all gets down to what you want to do with it? Keep it "forever" or sell it later. If you keep it, you do what you want. If you want to sell it, you do what is in the best interest for a higher market price.
There are plenty of people that will pay a high dollar for a solid plane Jane because THEY want to customize it as compared to a palne Jane that has already been customized.
Go figure??
Always remember to have fun with your project!