What parts do I need to fix temperature gauge?

What is your question?

I have a 1991 Chevy S10 pick-up - it has two doors and the gauges are standard (not digital). The temperature gauge bounces around but mostly sticks above the highest point 260. Check Gages light is on, but engine is not overheating. Gauge is at 260 even before you start the engine.

How long has your 1991 Chevrolet S10 had this problem?

Over 1 year