I would recommend, using several 1/2 socket extensions snapped together (can get some really big one from p-auto dirt cheep) with a large socket on one end (can remember the size I used). For the passenger side seal (assuming vac engaging model) you tap the seal into the engagement fork housing.
For the drivers side seal you tap the seal into the diff pumpkin. Installation is the reverse. I would not push the thread rod technique its a pain in the butt!
Regards,