To an extend, the moniker used in Real Estate values also applies to collector cars: Location, location, location.. There is a 20+% spread in value/price if you consider this.
And then, timing. If you sell your car exactly at that time when several people are looking, you will be able to realize a higher price.
I don't know the car of course, but from your description, anywhere between what you are asking and what Rolf-Dieter said seems to be a fair price.
Although, you may have to let it go for 50-55k if you want to sell it and are pressed for time.
Restoration jobs for these are extremely pricey and if someone wants to buy it to turn it into a perfect car, they may not want to spend that much.