YIKES
1....Make absolutely CERTAIN that voltage regulator is grounded
2....Pull both field wires off alternator and check continuity of alternator field terminals to ground. Should be "open" or infinity
3...Pull VR connector off, and check continuity of green field wire at alternator to ground. Should be open.
4...Make CERTAIN you have a ground jumper from either the battery or the engine block to the body. I like to use a no 4 "eye to eye" starter cable from the rear of the driver side head to say, a master cylinder stud
Access 12V "run" going to ballast. Clip your meter on there and the battery POS post. Turn the key to "run" and take a reading. Should be VERY low, the lower the better, less than .3V (3/10 of one volt). ANY voltage shown here is ADDED to the nominal 14V setting of the VR, that is, say your read 1.5V in this test. If the VR is properly regulating at 14, the 1.5 will cause the battery to "run" at 15.5
If all the above checks OK, replace the VR