Where can I find a speedo and tach bezel, the part that they mount to, for a 79?  Mine melted.

Are you talking about the clear plastic lens or the housing for the speedo/tach?

If just the clear lens portion, most of the restoration houses like Corvette Central, Eckler's and Corvette America carry it. If you're in need of the actual housing, check Ebay and see if someone is selling one from a parted out car, or contact some of the Vette suppliers that specialize in good used parts.