Square nuts and bolts.

Unknown

I'm looking for  a number of 5/16 bolts with
square heads, and square nuts, as used in the running board mounts and rear
fenders on '28 -'29 Hudson and Essex.  The square nuts clamp into special
cradles on the inner body for the back guards (fenders), and the square-head
bolts fit into the special  brackets under the runing boards, and go
through the chassis extensions.  Can anyone help with a source
please?  Incidentally, is it only us in the colonies, or has everyone been
banned from accessing the classicar forum and chat group?

Geoff.