John,

There isn't a wiring diagram that I can find for a '51 online. I don't think you will see any measured draw on the ammeter when you mash the starter...the meter needs to be between the battery and the load.

Your wiring flow is correct. Most loads come off the ammeter and it gets it power from the battery (or generator).

To be honest, I am not sure what the problem is you are trying to solve. I thought you trying to get this rig running after many years of retirement.

Stuart