There are procedures in my B757 manual for Dual Engine Failure. I would assume it's the same for a B767. I'm a bit confused by your question. The RAT provides hydraulic pressure to the center system for operation of the flight controls, at least at speeds above 130 kts.
So help me with my confusion. What leads you to conclude that there were no procedures for a dual enginge out? As you know, the RAT only provides hydraulic pressure. It can't help the fact that they ran out of fuel. The procedure is designed to attempt to re-start one or both of the engines, while ensuring the RAT is deployed to provide hydraulic pressure to the flight controls. With no fuel, the engines obviously won't re-start, so you glide.
However, this incident occurred in 1983, in the very early years of the B767. Perhaps at that time, there were no procedures for a Dual Engine Failure. It wouldn't be the first time that the manufacturer has had to develop procedures for scenarios that were thought to be virtually impossible.