My Test Mule

Good for you.

Now. If you really want to check the alternators, bring the rpms to 1250 and put some load on them.
Since you don't have a carbon pile, turn on the parking lights, then the headlights, and finally add the heater fan.
Check the ammeter at each step. If at any step the meter shows discharge, the alternator output has been exceeded.
Also measure the voltage at each step. You can measure at the battery or at the alternator. I think alt output voltage would be better in this case as it won't be effected by the voltage drop changing with increasing current.