1989 Chevrolet S-10 Gauges on dash going bonkers

Thanks for any help you can provide.
My oil pressure gauge indicator started bouncing, then will go all the way up and stay there for awhile. Then it'll start bouncing again. I'm having the same issue with the speedometer, Bounces a bit then it will go to zero.
I'll get the check engine warning light along with the service engine light coming on. All these little things are happening intermittently.
I've checked the connections that connect to the computer under the passenger seat floor board.
I'm getting kinda used to seeing these lights on, they're not giving me accurate readings, which kinda makes me nervous. The gas gauge at least stays constant, but is wrong, as if it gets to 1/4 tank, I'm out of gas. At least that problem has been happening since I bought the truck, and still happens even after I replaced the float assembly, in the tank. I think it has to be a main connection someplace, Other than that, I've run out of ideas.
Thanks for your suggestions,

Buddy