7) Dwscr said that the bolt head that I have on the lower control arm was the grade markings for bolt hardness. If the bolt head had a 9.8 or 10.9 then the bolt would have been a metric and a later model. (might be good information for someone else in the future looking for a similar question). As you can see my bolt head has a circle with lines radiating around it. And when I go to OPGI website, the replacement bolt for 1970-77 Monte Carlo has the same marking (
https://www.opgi.com/monte-carlo/197...nents/CH21441/ ) .