Since your vehicle is a 1949 the bushings will be pinned. The one piece bushing w/seal is the way to go. Remove only the front bushing but drill pins out of both since the okie bushing will push the rear bushing and seal towards the rear end when installed. This can be done without removing the entire assembly and putting it on the bench. Once you disconnect the U-joint and drop the torque tube you have room to work. The okie bushing is driven in with the seal towards the rear end because the U-joint yoke slips into the bushing end. Protect the seal from the driveshaft splines as you insert, lube with a bit of gear oil. My okie already had the seal installed with the closed side towards the rear end. Use sealer around outside of new okie. Depending upon the fit you may/may not want to carefully re-pin it. Insert new okie to be flush with end of torque tube. As noted by 31,32,33 above be sure that the torque tube seal is the problem since this is not a simple project. If the differential is overfilling then the torque tube seal is the culprit. Since you have to disconnect the U-joint it can be inspected for wear and you'll need new ball gaskets for reassembly. Lots of other info posted in this forum under okie bushing. Good luck!

Ed