Oil pressure gauge reads "off the chart"

[KMACD71]

I've decided to try to fix one of my nagging electrical issues. My oil gauge is one of them and for a while now it reads well past full when idling and the needle practically disappears when I hit the gas. I believe the problem started when changing my wiper motor or something under the dash. Is there a ground wire or something I may have knocked loose? The truck is a 71 with a 350 and has always run fine. Anyone experienced this before and know of a remedy. Thanks.