IIRC, it was 5/8" thick, oil/heat/ozone resistant high density stuff. I sandwiched it between the OE metal parts, drilled the hole using a holesaw & low speed.


My \'64\'s in the Gallery
Pictures in my Photobucket
1964 C10 Custom Cab 350/700R4
1964 Suburban 350/700R4
1979 Ford F350 4x4 400/c6