Depends what you want at the end. If you spend a lot of time and money restoring a mass produced cheap family car then that is what you still have at the end of the project. Typically, spend $25,000 restoring something worth $7,000 - $10,000 when finished. Think of your expenditure as the cost of your hobby, not as value adding. Too many motor hobbyists confuse the two issues. I have heard many say that their pride and joy has cost $xx,xxx to restore "and I want to get my money back". Sorry, Mr. Advertiser. your 1950's pusbox is worth a fraction of what you spent on it.
Really, many mass produced cheap cars are not worth restoring. They have no great technical merit, no interesting competition history, never owned by the rich and powerful, etc.
The classifications are veteran (pre 1919), vintage (pre 1931), Post-vintage Thoroughbred which is a term used by the snobbier vintage sports car clubs and not recognised elsewhere, Classic Car which is make and model on the Classic Register commenced by the Classic Car Club of America and now accepted by the world wide federation of Classic Car Clubs. All others are just old cars.

