65 Chevelle SS clone with original idiot lights in the dash. I installed aftermarket mechanical gauges. I removed the old sending units and used the water and oil ports for the mechanical gauges. What should I do with the original wires for the sending units? If I just cap them off will the idiots lights stay on?

If you cap off the wires the oil light will not come on. The temp light will as you start the car but as soon as you release the key it will go out.