According to my part number service guide, that number IS for a '75 four cylinder car. Might your radiator have been changed in the past? There are two shrouds for the V6: 8146A, for the standard V6; 8146B, for the air conditioned V6. The listing title is "Cap, Radiator Shroud, Fan", but my guide doesn't show an actual shroud. It shows only the little finger guard.