Emergency brake upgrade problems

['65 chevy lover]

Trying to up grade my '65 C10 emergency brake to the same as the '66, but the cables aren't quite the same. The 'prongs' on the end the cable that inserts into the drum that keep the cable from coming out, don't keep the cable tight. There's about 1/4" - 5/16" difference in the end of the cable. Has anyone else had this problem when trying to upgrade from '65 to '66 emergency brakes? Below are pics of the cables. It's kind of hard to see the difference, but it allows a lot of slop. Is it possible that I was sent the wrong cables from LMC or, is there a difference in the '65 and '66 brake drum or, is it even something to worry about?
Thanks for any help, I'd be very appreciative of it!