Logan5

I just bought a 98 dodge 3500 cummins 5.9 this weekend, got a great deal, much work needed of course. I see many of my troubles are common here. but I am having a problem with some of my dashboard instruments. I first noticed the fuel gague fluctuates from 3/4 tank to E every 15 seconds to 1.5 min's or so. this causes the low fuel light and tone to sound each time this happens. I also noticed today that the Oil pressure gague is doing the same thing, and causeing the "check gagues" light and tone to sound. at first I was not sure, but then the oil pressure gague went back to normal so I did not shut it down. it does not happen at the same frequency as the fuel gague fluctates. I checked the wires going to the tank and they are not loose or damaged. could both of theese problems be related to the same short/fault? if not, any ideas how to track it down? I have multimeter and have advanced electrial and electronic understanding. Thanks in advance for any help, Let me know Logan