Selling a car seems to be so difficult!!
For what it's worth, when I read your ad the first thing that popped into my head was the fact that it hasn't been on the road or driven for at least the past several years. You mentioned the trans was rebuilt "several years ago, and doesn't have 100 miles on it". To me, thats not a good thing. If I were looking to purchase a car in the price range you desire, I would want it road ready, knowing that the seals in the trans aren't dry rotted and going to give out in a couple hundred miles. It seem to me by your description that it has not been driven much over the past 25 years, and with the amount of things that need corrected, replaced, or repaired, your price is too high for a project car that has not been driven a lot lately, if at all.
Details... people that are looking to buy cars right now like clean, crisp and road ready!! When things like the horn button, radio, door panels and such are missing, it makes the car seem like a pieced together car, even if it's not. They can't see past that to what should be your biggest selling point...that it is a rare car and is worthy of a restoration. No mention in your ad of how many 360 automatic Dart Sports were made, and no documentation to back up the fact that it is even a real 360 car!!
If you want to demand the big bucks, you need to have a description that relies on this cars credentials, and after 25 years of ownership, you should have been taking advantage of your time with it to fill in the gaps. Put the seatbelts back in, find a radio, horn button and door panels. Yes, you'll have to spend money to find them just to sell, but if you had spent a few $$ here and there over the years to fill the holes, it would not be such a big hit on your $$ now.
When I read an ad that states how much has recently been replaced, I don't say good, one less thing, I tend to say that it needed to be replaced to make it what it is right now!! Oil just changed?? Great, but how long was the old oil in there, and should I have to pay extra when it probably needed an oil change anyway?? Get my point? You would have to reduce the price had it not been done, but usually doesn't happen the other way around with maintenance items!!
I hope you sell the car if that is your intention, and maybe a little time as your project over the winter to correct some things will help with the sale, maybe come spring at the latest, but I too agree that you have to be patient and stay in it for the long haul!! Geof