The "broken bolts" are actually rivets. In order to remove the drum from the hub, those will either need to drilled out, or have the heads cut off and driven out. As BDammers47 stated, it's best to remove the drum and hub as an assembly from the truck to do this to prevent damage to the bearings/spindle. Once the rivets are removed, the drum should come off the hub with little issue. The rivets do not need to be replaced, they are only there to hold the drum and hub together when the truck was originally built, they serve no purpose after that. It's essentially the same as the speed nuts that re found on late model cars.
On a side note, if you are planning on using an aftermarket wheel, the rivets should be removed, as they will cause a wheel seating problems. Aftermarket wheels do not have the "pockets" to clear the rivet heads.
