If that motor is from a truck, it, like Jerry said, is a 255/6 and is basically a Merc engine with the 4" stroke crank rather then the 3-3/4" stroke 239cid Ford. The bigger engine is worth a bit more then a standard engine as it will go to the fabled 296 cid more easily (3/8 x 3/8). The bigger engine will have heads that have 8CM or something similar while the 239 will be 8BA