I'll dig up Roy Lane's book, as it mentions the March. Plus I'm an expert on this as I have the Scalextrix version.
From memory, March lent the gearbox to Lane and he entered several National events, and probably won then. It did seem to work, but hillclimbing benefits from the extra traction. However, it didn't seem any quicker than 2WD, and was unreliable (underdeveloped), so the car was converted back to standard.
Having 4 wheels at the back would have caused scrubbing on tight corners, like an artic trailer round a sharp corner, so it must have had loads of understeer.