My experience from having painted two Datsun 510's with lacquer (late 70's) is it took a minimal of four quarts. I bought it that way in case I could return a full quart, but I don't recall ever doing so. I'd think that buying by the gallon would be more economical? I'd think there is a general coverage rate for any specific paints and a tape measure will tell you the surface area to be painted on your Pinto. As Dwayne already stated though there are significant variables. You might want to try seeing what the Duplicolor (know Pep Boys carries it)" paint it yourself" information provides. That should give you a ballpark idea of the amount needed.