I have a friend that just sold one for $12,000 that was a total restoration car. Right now, the market is very soft, and what used to bring $20K, now brings a lot less. It is a buyers market, and condition and originality are two of the key things that buyers are looking for. There is no shortage of any Model A cars and trucks, so buyers can be choosy and will only buy if they can get a bargain. The more rare the model, the more that it will command in price. If you watch the Barret Jackson auction from year to year, you will see that the last years auction prices were down considerably from previous years. If you expect to get top dollar for that truck, you will need to detail it to perfection, and be ready to prove that everything is original to the truck since new. Most of these older Model A restorations have had the engine and / or transmissions changed. The fellow that I mentioned in the beginning can tell the differences between each and every year that they were produced, and when we come across a restored one at the swap meet, he will point out to me which parts of the car are wrong for that year. I just picked up a classic car calender at the Ford dealer. There was a picture of a 1950 car in there, and he showed me where the restorer used 1949 parts on it. It looks great, but it isn't all original. I can do the same with Corvair's, but to most people that all look alike from 1960 - 1964 and the second generation 1965 - 1969. Many parts will interchange, but they are not original to the car. Serious collectors know the differences between years and models when it comes to paying big dollars. It is all in the details...
I bought this one of a kind factory prototype Chrysler last year, and even though they only built one, it isn't super valuable. Rarity only counts if someone wants it...