[KevinW]

If its a fibreglass dashboard and the fibreglass is too thick, you can buy a small hole-cutter for your drill (kinda looks like a spike sticking out of a flat blade) - usually used for cutting holes in wood/board. Drill from the back of the dash with dash pressed down on a scrap piece of board/wood. Drill slowly, stopping frequently to check, and you can reduce the thickness of the fibreglass surrounding thr thread to an acceptable level.