That bolt sure looks a lot like the retaining bolt that holds the rocker shaft to the rocker shaft bracket.

Not sure if the washers go with it or not.

Best Regards...
Attachments
Rocker Shaft Bolt 02.jpg (322.18 KB, 163 downloads)
Rocker Shaft Bolt 01.jpg (288.41 KB, 161 downloads)
Rocker Shaft