Does anyone know what the head marking and style of the long bolt that goes through the Bell Crank (Linkage assembly) for the Power Disc brakes looks like. This is the bolt that attaches through the long sleeve and is the pivot for the linkage. I am assuming there may be several variants depending on year. Was this a standard 3/8" bolt or a specialty bolt with longer shoulder and short thread section.

This one is from a 1968;

The head marking on my '70 is different, but even with a flashlight I have not been able to get my camera to focus on it.

I figured they might be different year to year. But yours does have a shoulder shorter than sleeve. I saw one on a search with shoulder as long as sleeve. I have a bolt with C and H similar to the brake pedal bolt that attaches to push rod, so I wonder if they may be correct too. Thanks for help.