This is a re-occuring question that I hear about a lot.
The simple answer is to do what fits your intentions. In general, only put things on your car that you can change (back to stock) in a day or two at the most.
As time passes, originality seems to be the thing to do. When you see a '55 T-Bird with slotted wheels, and primer spots, what do you think? "Gee, too bad that car isn't original--it would sure stand out with today's cars".
When you drive your Cs in public, you are representing the CS heritage. it makes a greater impression as it was. Yes, I like to promote vintage Shelby parts, but it's a tasteful, and period type of mod.
In the meantime, get any and all parts that make your car complete, whether you plan on letting it go or not. At $30K-49K these days, having those parts might be worth the additional $5-10K to bring it up to those values.
Paul N.