My buddy has a 1988 GMC regular cab shortbox with the 350 motor. The truck seems to run great, but his oil pressure guage is really weird. When the truck is idling, the oil pressure guage reads almost zero, but when he revves the truck up it reads a more reasonable pressure.
Is the oil pressure guage malfunctioning, or is he looking at some more serious problems. I told him to get it looked at, but he is dead-set that it's the guage. Either way, no one wants to take chances with oil pressure!
Thanks.

I would suggest you install a known good mechanical oil pressure gauge into an oil galley and see if that confirms the low oil pressure reading. If pressure check OK then start looking for a bad oil pressure sender, a wiring issue or a gauge problem.

just get a external pressure guage, they are really cheap and available at damn near all auto part stores. that'll let you know if you have a oil pressure problem. a simple check can save you having to buy a new engine or truck later.