You mention 2 different philosophies...original and not original.
Personally I would go by how much original stuff you have for the car at this time.
If you need to swap on (meaning BUY) a lot of original items (air cleaner, carb, seats, whatever)...then it probably would be more economical to go lightly modified.
If you have a bone stock car (90%...95%...100%)...then i would keep it all stock.