Tim,
I just happen to have my car up in the air.
As I recall, I used flat head screws with aero-nylok nuts and fabed up some tube type bushings on either side of the assembly. I came in from the side with a hole through the tunnel and then used one of the lokar "L" brackets on the other side. It is very sturdy (my tunnel is 1/4" fiberglass)
Hope this helps,
MIke 'monster'