I sourced the ABS from TAP Plastics out in Santa Rosa California, Mike.
They have EVERYTHING! It's a little nuts. If I had a perfect OEM panel from a 1960 thunderbird, I could have had them form it to exactly that shape. I didn't have one so I thought of a new design. I bought two sheets of black ABS plastic for about $75-80. Pricing was a little steep but it's going to last a long long time now. Before going with ABS, I took the original panel and fiberglass re-enforced it so i would prevent the panel from breaking and warping any more. ended up not working out due to it fitting incorrectly.