bb, the MB had a Dana model 27 in the rear. It has an outside AXLE TUBE diameter of approx 63.5mm. The front axle is a model 25 and shares the same basic dimensions.The tube is the component pressed into the center section. It is where the U-Bolts go over to hold the axle to the spring. Is this the dimension you are looking for? If so, no your not in the ballpark!