Technically almost everyone's car is modified ~ if you add wheel valve caps, that's a mod, your favourite bands sticker on the rear window, that's a mod etc
Personally I think a proper restoration of any car is a bit naff really ~ always best to improve on things where you can imo.
Used to work as a classic car restorer. Mainly on MG's, Austin Healey's and a few Triumphs.
We did have other cars in for work though including a Ferrari Dino and two Aston Martins that where having full restorations ~ a DB6 and DB4 convertible. Every car we did had something different from what it would have done from the factory. On some it was just stainless steel bolts or other more modern rust resistant components but others had completely new braking systems & power units which was always for the best.