gauges on dash

Check the grounds.

It is the one thing they all have in common. If the power to all those gauges is consistent, it makes sense that there is a bad ground.

Second most likely problem is the key switch itself. Use a jumper wire to go from the hot to the run terminals on the back. That will by-pass the contacts inside the switch.

Let us know what you find.

while it is running you might want to stick your hand under the dash and move the wires  around some to see if there is needles on the gauges start jumping around. yes most likely a ground but it could be a resistance problem on the hot side.