"Too far gone" means different things to different people. Anything can be fixed. Even if all you have is a dataplate and VIN. The question becomes, is it worth it to fix what you have vs starting with something that is in better condition. There are basically two arguments for restoring. First - does the car have sentimental value? Has it been in the family since new? Was it your first car? Did you bring your new bride/kid/diploma/date/keg of beer home in it? Cost tolerance tends to rise in those situations. Only you and your sponsors can make a decision about what is appropriate - how long the restoration will take and how much will it cost. Second is rarity. Is this a rare combination of options/colors? How many were built just like it? Is it particularly desirable (and therefore resellable)? What are the current market price points for your particular case? Are they trending up/down/flat? This kind of decision is more financial than emotional, and if you are looking to eventually make your money out of the car, you will need to be cruel in your assessment. Restorations are ALWAYS more expensive than the first estimates, and you can wind up underwater pretty fast.
A third consideration, once you have sorted out what you want to do about one or two, is to decide what you want when you are done. A daily driver, a local show car, concours trailered? This will have the most impact on eventual cost.
Whatever you pick - enjoy the ride!
