I purchased this one from rock auto, FAIRCHILD KF100613 Belt, Channel, Seal Kit Info
Left & Right.
I have read good things about the bronco graveyard kit but with the shipping to Canada, the kit was expensive.
Install was fairly straightforward, I used a few tips from the service manual though.
1985 Ford F-250, 6.9L, Auto C6, 4x4 208F, Extended Cab