I've got a '66 Impala that had a really bad dash pad too. It had chunks missing out of it as well as all the cracks. We built it up with foam insulation wherever it had gaps and ground it down wherever it had warped up. Then we took thin poster board and taped it over the entire surface to make everything smooth. Then we stretched vinyl over it and it looked almost like new. I already had the materials lying around so it didn't really cost me anything to do it. (The reason we used the poster board was that we had tried to stretch the vinyl over the pad without it but every small flaw underneath still showed.)
