Adding an alternator or generator

[bbbuuuggg0]

I was wondering about adding a alternator or a generator to my '59 johnson 50hp. There is a bracket on the left hand side (opposite side verses starter) of the motor. Could anyone tell me if this was an option or what part number alternator it would be so I could go buy one(most part stores ask for OME#). Also do they run off a belt or off the flywheel?