Transmission mount questions

Working with a transmission mount from a 70 B body 4 speed car. Would like to know how to read the date code on this. Also, is there a way to repair a broken of stud on one of these ?

The round M indicates a newer repop.

Drill and tap for a double ended stud?

ok, I can't say the mount is original to the car since I didn't buy the car new. I bought the car in the early 80's and it had been off the road for several years before that. So, are these mounts date coded ?

Thanks!

The circle for the 9 with dots around would be the date weeks and year, but since Mopar performance type 79, 89, 99?