I am looking for a source for some bolts that are used in a couple of places on a C3. They are used to attach the bumper extensions onto the front of the frame, attach the convertible frame, attach the hood to hinges, etc. where the holes are slotted so you can adjust position the and lock into place. These have a washer attached and the washer is cup shaped (like a Bellville washer) so that the edge digs into the metal when tightened. It keeps the parts from shifting like a flange bolt would do.
I tried Fastenall and Mcmaster. I used to have an Auveeco catalog but can't find it. I did find a picture.: