Not all owners of classic cars think in the same way. Some prefer to keep them original (patina and minor issues), some completely restore them and some restore them and also do modifications. All three require the love and attention to detail of a classic car collector. No matter his preference the commitment, effort and knowledge associated with this very involved hobby is admirable.
An original vehicle is one that has been maintained so well that it has all of its original factory specified parts. Their parts have been mostly fixed rather than replaced and if they had been replaced at one time it will have been with the original part intended for the model from the exact year of its introduction. To determine the originality of a classic, enthusiasts look for "matching numbers", serial numbers that are stamped on parts throughout the car that match each other and the number originally associated with the car in its year.
Pros and Cons
Original vehicles are extremely hard to come by. To produce one takes the most time and money because the original parts are as rare as or more rare than the car itself. Because of the lack of availability of models and their parts, many car owner's claiming "original" are actually restored. A true original and a restored vehicle should look the same and nearly operate the same, but because of the difference in original parts vs. re-manufactured parts, the prestige and value of a true original is significantly higher. The value of the three types of vehicles fluctuates based on the changing demand of collectors just like many consumables, but original vehicles, even in their shabbiest appearances can sell for 35% more than their perfectly restored opponent, a reason why you'll find a lot of speculation on which route to take.
Restored vehicles are made to look and drive like they did the day they were introduced to consumers. Their owners however, choose to replace parts with factory refurbished remakes of original parts. Using the original as inspiration, a car restorer will match the interior, parts and paint as closely to its glory days as possible.
Pros and Cons
Because restoration parts are easier to obtain and the restoration route creates more of its kind, this vehicle is less rare and often less valuable than an original. This is also the reason a collector can achieve results faster and perhaps joyride in his car sooner and for longer, a pro that's hard to argue if you're familiar with the work required of an original. As previously stated, the monetary value of a restored is less than an original in many cases, but there is value in having the most fun in your car and if that's a high priority for an owner than this is a fine choice!
Resto-mod is short for restored and modified. These vehicles are the furthest from originals. They are restored and often "modernfied" if you will. Some owners choose to enhance the engine, make it more fuel efficient, or add modern luxuries like a preferred sound system or safety features.
Pros and Cons
The sky is the limit for an owner with the freedom of modifications. He can build his dream car! Resell for these cars is difficult though and the return could be even less than was put in it so this is the biggest pit fall. The reward is grand and the risk too, is grand, but for many this is the perfect fit for them. The value of a restored and modified vehicle is very unpredictable because the vehicle has been tailored to its owner's specific tastes and he'd have to find a similar buyer, something to consider when choosing this method and while choosing each modification as well, if reselling is an area of importance at all.