The greatest advantage I see to a 3 wheeled setup is the ability to register as a motorcycle, which gets you around a lot of regulations that only apply to 4 wheel vehicles. It's a great solution for home-built electric or alternative fuel vehicles. If I wanted to do this on something with too much power to just use motorcycle running gear, I imagine I would look at using a locked differential mounted in front of a rather wide rear tire. A sprocket on each side of the differential would drive a sprocket on each side of the rear wheel via a heavy chain (or dual drive shafts if you wanted to get fancy and spend a bunch more). Driving the wheel from both sides instead of just one as on a motorcycle would add a great deal of strength and resist torquing the wheel to one side, and solves the differential issue by allowing you to use a car diff.