Many classic cars for sale for restoration demand a premium for "Completeness".
After many years of buying and restoring, mainly british sports cars of the 60s and 70s, I have this to share.
Most of these types of cars now have a very good parts supply network through Moss Europe and others. You will find almost every body panel, mechanical, electrical component and trim item available new at suprisingly reasonable prices. Therefore if you are buying for complete restoration, unless you are completely rabid about restoring original parts, you can save a lot of time and money by buying a part dismantled car, say with no outer wings or trim items missing.
This way you are not paying for parts you will have to remove and throw away later.
Just a thought.