Many times you are looking up a part on a Website that sells OEM type parts.
Today I found a mistake.
If you have a 1977 or 1978 CB750K the Parts diagram breakdown shows the brake reaction arm for the rear brake facing the wrong direction.
It is the tubular type brake reaction arm.
The end with the slanted cut off faces forward. Not backwards.
I was assembling my bike and the brake reaction arm would not fit.
So I consulted my Clymer workshop manual and it shows a clear photo of the attachment point of the brake reaction arm on the rear brake hub.
Page 174 Photo #17.
Also make sure the lever arm on the rear hub has the sheet metal tab with arrow facing the matching arrow on the hub casting, when the brake is not actuated.