Either the 7.25 was upgraded over the years or something is wierd. I have seen several LOADED 73-76 slant six 4 door Valiants and Darts with the 7.25 axle. They theoretically should have had the 8.25 if durability was a concern. I stick with the towing package theory. HD axle, Trans cooler in HD radiator and 7 blade fan with fan clutch.