Rearend id in fender tag?

My late build date 1973 Dodge Dart Sport 340 (low compression 340) 727 column shift, deluxe bench (bucket seat top arm rest center deluxe bar at pattern sewed up) A/C -heat. AM all black insides with full interior in trunk since had a fold down seat, and the 8 1/4 321 sure grip. Gave it away when I put the 8 3/4 in.
I do not think they had 323 were 321