The whole axle assembly could be made to work. The 55-62 1/2 pumpkin will interchange with the 41-54 rear axles. It basically converts the older axles to the open configuration. One advantage for this conversion is in keeping the factory rear brake configuration. You won't have any problems with the parking brake cables needing to be modified.
That 63 rear pumpkin might work too, but it is likely a gm 10 or 12 bolt truck rear, and not the eaton ho33 rear the earlier trucks had.
