I’m looking to see what these numbers mean.

They are on parts in a 3.55:1 12-bolt I think it is a KJ but I have to check that.

On the ring gear (The gear has 39 teeth) is stamped.

K45 K45

And

1 12 10

On the pinion is stamped;

5383008-11-39-GM

what is the stamped in number on the passenger side facing front of the axle tube?

My old 12 bolt was a KJ. That stands for 3.55 large ring gear.

and the part number you posted has 11-39 at the end.

39/11= 3.545

Sooo you have a 355 gear.

Thanks for the info -- I've been looking for my notes but I can't find them and with the rear painted and in the car it is difficult to get the stamping. I don't even know if the numbers would be visual anymore with paint.