My '95 Silverado P/U Oil pressure gauge is erratic..... it constantly pegs all the way over, then back down to 0, and back over etc..... occasionally it will begin to read "normally" for just a bit, then back to the erratic behavior....it'* irritating because when it goes to 0 the red dash light comes on to "Check Gauges"....... any ideas..... sending unit bad etc..... ??

It sure sounds like a replacement Delco sending unit is in order.
What engine/ how many miles on your PU do u have? Is the oil on dipstick at full line?
But it sometimes can be electrical connections as well.
It may be best to hook up a mechanical pressure gauge to see where it truly is at.

i think on all the engines for that one the sender for the gauge is the one by the filter and to me it sounds like that could be the issue, not a real good way i can think of than just replace it. as mentioned get a delphi or delco one (rock auto has good prices on oem stuff) just make sure the plug looks good and dont use any sealant or tape other than what may come on sensors, because the readings are based on resistance to ground which is the block electrical connection