Are you sure that is off a 73'? I thought the filler cap was on the right side when looking at it like your picture. I could be wrong. Maybe somebody could chime in or take a picture of the date stamp on the back. Does this differ from Bav to CS? I have a later head on my motor so not sure the date on my valve/rocker cover but mine is different. All the 73's that came up in search had it on the right, not like this one. You have me confused now.