Any part of the chassis is a ground, you just want to find somewhere where you can attach straight to the chassis.
http://i1184.photobucket.com/albums/...7/IMAG0049.jpg
Looking at that pic it seems like you may be better off finding a different bolt if possible, it looks to me like the hinge is bolted to the chassis and you would only be able to put a ring terminal ontop unless im mistaken.
i prefer to connect directly to the chassis rather than on top of things, ill try and draw a pic to explain.
This is how it would be connect with that hinge, would have to go through the hinge instead of being connected straight to the chassis.
http://i1087.photobucket.com/albums/...strys2/fgf.png
I prefer to do it like this
http://i1087.photobucket.com/albums/...trys2/fews.png
Hope that makes sense, i cant draw shit well in paint

