The Stovebolt Site Forums The Shop Area Paint and Body Shop Small Hole In Dash

You could try some fiberglass body filler and a piece of fiberglass cloth.
Apply the filler to the cloth then stick it to the back side of the dash. After that sets up apply a coat of fiberglass filler to the backside to give it more strength. After that sets up sand down the front side and finish it off with "bondo".