Those numbers are on my 69 rear, ..if ya look its the numbers 1 thru 9 and 0 probably an internal thing with the foundry that cast the center section
on the front side on the bottom web is another set it is the actual cast number and is shared with 67-69 67 is mono leafs 68-69 are multi its an easy way to tell..heres pics
that code on the front side tells ya date, gear,and which posi if originally equipped
