[Steve Siedlecki]

Blackjack,
What I would suggest is get a couple of scrap sheets of plywood. Trace around the existing hole of the gauge you wish to make bigger. Drill a pilot hole the same diameter as the pilot drill for a hole saw for the new size. Then realign the scribed hole to the dash hole.
Then sandwich the dash between the scribed hole and the other scrap piece of ply using clamps. Then carefully use the pilot hole to drill completely through the dash. The wood will support the dash and give you a real clean cut.....
Steve