[Pat Roche]

Also, by placing the idlers above the driven sprocket on one side and below the driven sprocket on the other side, we could have both our motors running the same direction (which is much more efficient than the worm gear solution posted above, since worm gear efficiency is around 70% at best, while sprocket efficiency is around 97%).

With worm gears the efficiency really depends on the maker (if commercially purchased or not...we used a Boston Gear worm reducers this year and the had about 80% efficiency. What would work best if you can find them is planetary gear sets. They have about a 97%-99% efficiency (depending on what you get).