Just Dashes in Van Nuys, Ca offers a complete restoration of your GT dash. Just Dashes are on the web at www.justdashes.com. They strip it down, refoam it, vacuum form the vinyl and you have a new dash.
They did the dash in my ´69 GT 10 years ago and it still looks new. Cost was ~$500.00. It sounds high, but when you take into account your time and material cost it is not that bad. Uncracked, used 30+ old dashes will go for $250 to $300 and they will crack.