Small Engines (Lawn Mowers, etc.): Re install cover, video look, engine parts

Question
My son took apart an old cast iron 16hp briggs model 325430 and remove the cover on the mag side of the engine it includes some gears and a counter weight how do know where to position the counter weight?

Answer
Can you send me the engine type number as well so I can look up the engine parts list?

This link shows some pictures of very old ignition systems.  Do any of the pictures look like yours?

Here is a video on You Tube on installing points:

http://www.youtube.com/watch?v=iJArptA6Vco

Does the engine in the video look like yours?

Eric