Last night, I pulled the headers from my 74 and i didn't disconnect the battery. The header touched my alternator and sparks started flying.. one of the wires on the back of my alternator looks burnt & corroded.. did i just short out my alternator?
It is unlikely to hurt the altenator, but shorting out the wire and burning the insulation on the battery wire may burn out the fusible link in this wire to the battery (which is supposed to prevent this wire from burning). I wouldn't bother testing the alternator, but replace any burned wires and or fusible link.
You will know soon enough after you replace any burned wires and start it up. The alternator is always hooked up to the battery, so basically you just shorted out the battery wire. You must be missing the little rubber cap that covers the exposed battery wire, which would prevent this from happening.
If you had shorted it with a wrench, you could apply for admission to the "welded wrench society".