Here is my thought on the subject. In 1998 I tore apart my 1970 GTO and did a full restomodification. The car made it into several magazines and eventually I did a LS swap. I don't drive that car too much because while not perfect, I am fairly paranoid about door dings.
http://www.superchevy.com/features/1402-1970-pontiac-gto-ls3-swap/Last year I built a LS swap 1967 Cougar. The body was mostly rust free and the exterior has a ton of patina. I drive the wheels off that car and take it EVERYWHERE! Last week I drove it from WI to Memphis and it was no drama, despite going through rain and having drag radials. This car gets more attention than if I set my GTO on fire in the middle of Time Square.

Bottom line is that you have to decide how you want to use the car. If you want to drive it and not care about exterior, then don't go crazy...
Andrew