GM-GMC: 1984 GMC P32 step van, oil pressure gauge, voltage gauge

Question
I recently aquired this step van.  The gas gauge always shows full.  The temp gauge is inop.  The oil pressure gauge is inop. These three gauges are in a cluster with a fourth gauge, the volt meter, which works OK.  I have 12 volts going to the gauge pack-cluster and if I ground the "negative" side of the gauge it will go to "empty".  My concern is that I think this style gauge cluster is supposed to have an instrument voltage regulator that will reduce the signal voltage to a constant 5V instead of the 12V that I am getting.  The higher voltage might be what is causing the failure of all three gauges (fuel, temp and oil)... yes???  
Problem is also that I can't seem to locate the Instrument Voltage Regulator.   Any ideas?
Thanks!!

Answer
i have a gauge cluster issue on my truck a 05 gmc... the gauges went out one by one from left to right now only the temp gauge and the voltage gauge work. i have found that this is real common on gm vehicles of my year. as far as your gauge cluster goes i would try to have someone put a tech tool on your vehicle and start it up. this seems to reset it and in some cases fixes the issue. but other than that i have heard you have to replace the entire gauge cluster.