K Frame

The front of B and E K members are curved like the one on the right. Yours is flat across the front. NOT an E body K member.
View attachment 1715728864

There is something strange going on. Measuring it and posting the findings may help but that curve I mentioned is a clue.
Looks like the RH one in the photo is for a '66-7 B-body, and the LH one for the '62-5?