Josh,

Since no one has posted anything, here are some guesses (beware):

+ amp meter terminal connects to: alternator stud
This should be a fairly hefty wire - this brings the charge from the alternator to the Ammeter.

battery connects to: - amp meter terminal
This should be a fairly hefty wire - this one gets the charge from the Ammeter to the battery.

one wire (14 gauge?) of DA connects to one ignition switch terminal
This is the "exciter" wire - it signals the alternator to start charging. (This wire is not needed/used/found on a one-wire alternator, which "self excites" at 800+ RPM.)

second ignition terminal goes to coil
This is your ignition lead.

third terminal connects to headlamp switch with 10 gauge wire
If you are referring to a third ignition terminal, this might be a power lead to the light switch?

Are there other leads from the DA plug? (I think that one might be to a dummy light - an indicator light?)

I am not confident that my guesses are correct - where is Stuart?

Tim