8-3/4 centre section swap

For the most part, rumblefish360 is correct. However, there are a few 3rd members that MAY not interchange without some modifications. The '64 and earlier 3rd members may have a thicker or thinner thrust block than the one you plan to remove depending on sure grip or not. All the '57-up 3rd members have the same side gear size for the axle shafts and they fit all the housings but you may have to get longer or shorter axle shafts to match the thrust block. The '65 and newer ones don't have that problem...just the u-joint varieties.