On the specs... my car is an "E". I don't "think" there was any difference in important specs on drums for "B" and "E". Some were finned for cooling and some were not which affects outside diameter but not the "working" dimensions. I did double check the Y1 link and it is for 2.5" x 11". Good luck!

I finally checked my actual runout - one axle barely had .005", the drum (mounted normally, measured at the edge of the friction surface) had .038". The other axle indicated .012" – at that point I figured "close enough for now" and went and ordered some Challenger-spec drums from O'Reilly's. Hopefully when I put them on tonight or tomorrow that'll be the end of this mystery (otherwise Dr. Diff's getting more of my money for axles)

Check them to see if they are out of round before you use them.