The 2 shafts and several gears that make up the trans, along with the shift forks and drum, probably weigh a total of 20 pounds. The oil and water pump, as well as the oil sump, pickup, and filter, are located at the very bottom of the engine case. The rear housing contains the clutch (which drives the oil and water pump), the alternator (the stator is bolted to the housing, and the rotor contains the starter clutch), and the output shaft. You'll need to leave the upper trans shaft, clutch basket, and primary chain in place, as these drive the oil/water pumps.
Unless you want to make serious modifications to a Wing engine, a VW engine would be lighter and simpler...no cooling system, no trans, and fully self-contained. Just my humble opinion...