Mmmmmmm...?..

How about drilling through the outer jaw & inner jaw with a drill diameter of the bolt, drill the outer jaw a larger diameter to allow a bushing with the diameter of the bolt in it. Cut to desired length & weld in place. The bolt head would be a bit proud but unless you filled the cavity I cant think of a way to countersink the bolt head unless you make it a bigger job by making a big hole in the outer jaw & use a thick walled bush that gives a bit more meat for machining it out to accommodate the head.

Must be other ways but that's my first thoughts.