I was wondering if there was some type of sealant or something that was used where the bumper brackets contact the body in the rear. Any reccomendations?

I used a very light coat of silicon sealant around the hole on the bracket side and a rubbery (sorry - I don't really know what material they are made of, I found them at an industrial supply and they fit the inside washers perfectly) washer that was about 1/8" thick on the inside.
I had noticed a little rust under the original bolt leading into the truck in a couple places and decided to stop any further water getting in.

strip caulk made by 3M