Another way to look at it depends on what you WANT for the car, not money but its future.
You apparently have a secure, dry place to store it and as you said, it is a very rare car.
Two things to balance is how much you currently drive it and if you become unable to drive it, will you just park it and let it sit.
A running - driving car will always deteriorate, but less so if it is driven. So many people tuck car like this away and it just rots. When the time comes to sell it, people want the full #1 price for a car that will need completely new rubber, fluids, ect.... Unless a buyer has deep pockets and really want this style of car, its going to sit and possibly just sold last minute to get it out of the garage as the house has to be sold.
Not to be mean, but younger people with $$$$ are going to buy a classic Subaru to fix up than work on odd ball type 1960's car. This does not account for European or an Aussie buyer.
If you really love the car (which you do) and want it to survive, and the decision it purely up to you, there is going to be a time to sell it while it is running to the next owner who will care for it like you have over the years or you park it, and deal with the possible scenarios above.
Example - my son bought his classic car this way. A guy really liked his base engine - convertible, but the people coming to look at it wanted to modify it, ect. My son told him he wanted to keep it as is and use it as a weekend driver. They guy sold the car to him, even though he could have made more money, but he really wanted the car to be cared for by someone like himself. They still exchange card at Christmas.
If your going to sell, find a local guy who will occasionally stop by and take you for a ride - win win.