The value of a 1966 Ford Mustang is available online at NADAGuides.com, Hagerty.com and ClassicCars.com, as of 2015. The submodel, body type, engine and condition affect the Mustang's value. ClassicCars.com lists collectible '66 Mustangs for sale.
NADAGuides.com values a 1966 Ford Mustang GT two-door fastback with a V-8 engine at $43,000 for average condition, and that price spikes to $75,000 for a car in great condition. It values Mustangs with six-cylinder engines much lower.
Hagerty.com lays out the many types of Mustangs with their average values and value trends. It values the Mustang coupe at about $15,000 on average, which is the cheapest. Users looking for insight about future prices can use the trend feature, which is a line graph that plots various sales based on condition.