The short answer is that it is worth whatever someone is willing to pay for it.
Beyond that, estimating a value is pretty tough. Since there are so many variables, it is difficult to estimate your car's value based on recent ebay and national auction sales. Looking at one of these recently sold cars, you must ask how did the condition and quality of the restoration of it compare to yours? Was it numbers matching, is yours?
How about the color, value varies with the desirability of the color. 4 speed or auto? Documentation? The list goes on!
So a unrestored triple black one owner #'s matching 4 speed 15,000 mile AAR with all the original paperwork including window sticker and sales paperwork might easily bring over 100K. A white with green interior non matching #'s column shift auto with a so-so restoration, no documentation, many incorrect parts under the hood, might have a hard time fetching 30K in today's market.
So using that for a gage, your car falls somewhere between 30K and 100K in value.
Appraisers aren't that accurate in my experience. The last appraisal I had on my convertible in fall of 2006 was in the mid $90's. I have no desire to sell the car, but believe me, if someone ever had offered me over 90K for it, I would have taken the money and ran before the buyer came to his senses! At the time, I figured the car might bring 65K if I sold it, max. That would make the professional appraisal around 30% high. From what I've heard about other people's appraisals over the years, I think my experience is common. Think of all the ads you see over the years for vintage cars that say things like "appraised 25,000, first $17,500 takes it!".
And this market is a lot different than it was 4 or 5 years ago. Back then, people were buying cars first, asking questions later. Today it is much more a buyers market, a rare well documented original or well restored car still has a market, but it seems like anything that is not a prime example is very hard to find a buyer for.
Finding that buyer willing to pay top dollar is no easy chore, even when the market was hot. I've known a lot of people who have listed cars for sale in various places, with no luck, and ended up contracting with a broker to sell the car in order to get a high sales price, doing that you end up paying the broker a sizable commission though.
Anyways, that's my