I used the foam padding that's used under vinyl roofs. Seams and corners have 2" scotch tape on them to smooth out the bends and bridge the seams. I used hotglue from a gun to glue the foam to the fiberglass dash shell.
I also used the hotglue to glue the leather to the foam. Came out nice. The only thing I would do better would be to dye the leather a few more times to get it really absorbed. It's wearing off like around the ignition area.
Roscoe