The dash instrument brackets are secured with special knurled thumb nuts having 3BA threads. These are generally not available at your corner hardware store.

At 05:46 PM 6/12/2007 -0600, David Hoskins in Barwon Heads, Australia wrote:
"I have had trouble undoing and tightening the retaining nuts for the instruments. While they were out of the car, I made up some hex headed nuts, with a built in spacer, by drilling and tapping short lengths of small bolts with 3 BA threads. These can be attacked with a small socket or short ratchet spanner whereas the standard nut is difficult to grip with outstretched fingers."

One word of caution. For installation, tighten these nuts with fingers only. Over tightening with a wrench could distort the bracket or the dash panel, or could pull the riveted studs out of the instrument case.