A couple of things...
One, any car that has reached ten years of age (2002 and older as of 2012) is exempt from mileage reporting requirements. At the dealership I work at, if it is 02 or older we just simply write "Exempt" in the odometer area. It is reported this way during registration. In and of itself, this is not a problem and is perfectly legal and normal for older cars.
Secondly, due to the fact that the majority of our cars have only a 5 digit odometer, they tend to have rolled over, and when the mileage gets reported it shows as lower than they actually have. Honestly, unless the seller is an original (or maybe second) owner of the vehicle, I would always expect that the car has over 100K without some really good documentation. Really, how many people have cars that are over 20 years old and have only logged 40K? Ebay would have you believe that they are all over the place.
Now, as to the value of the car. I don't think that you can make the claim that this car truly has low mileage. Clearly, it had 39K put on in the first five years, it has likely rolled over at least once in its lifetime. So, the value is going to come down to how nice the car is, and how much someone is willing to pay (as usual) for a nice car.
Personally, I wouldn't be deterred by a higher mileage Fox that was in good condition. If the car is straight and hasn't been in any major accidents, that is fine. Would a documented low mileage car bring more? Probably, but it will naturally lose that value quickly if you start putting miles on the car. If I was buying the car as a collector, I would hold out for a low mileage car that I could store away. If I was just a guy buying a fun car, I wouldn't worry about it.