Does any one know anything about Voltage Regulator Instrument custer? wiring?

Ok my alternator is not charging my battery on my 1976 ford maverick. changed the alternator,the regulator and the wires that come from the two still not charging the better has been tested to its good. they said it may be Voltage Regulator Instrument custer harness? does any one know anything about this or know where i could get diagram showing me how to hook this up?