Looks like a late style 70 case and obviously is cast in Dec of 70. Also apears to have been assembled with a "711" pulley. Part number indicates it was built for 72 and later application. I'm with Chris on this one and would say it's probably a truck application w/air. Any paint marks still visible? This would give you an indication of amperage output. "Squarebacks" were pretty much universal beginning in 72 b/c of the change to electronic ingnition systems.