Yes I have a 350 SBC. I discovered this when I went to replace my timing chain cover. The new cover had the mark at 12:00. My new balancer was also at 12:00,but it was too difficult to see it behind the water pump so I used my old damper to line up the position for the pointer.


I then used the pointer to mark my new damper to cut the groove.

I don't know which car or truck this damper fits but there are more than one style. They are balanced the same, they just have the marks in a different place.