Dana 60 upper king pin.  See images for the exploded view, and #49 circled. These can be one of the toughest parts to replace on a vehicle.  Years of corrosion, and a factory torque spec of 500-600 lb/ft, makes this a bear to remove.  A 7/8" Allen head is what you'll need to remove this sucker, or a bit of 7/8" hex stock to go into the king pin with enough sticking out to get a socket onto.  Oh, you'll probably also need a breaker bar, your favorite bolt removal lubricant, a heat source, and a BFH (large hammer).

We offer all the individual parts to rebuild your Dana 60, or buy the kit with all the parts at a lower overall cost.