A factory Slant 6 with a 8 1/4 differential

my 74 slant six gold duster came with an 8 1/4. i took a slant powered val apart that had an 8 1/4 with 11x2" drums. not 2.5" drums. i thought that one was wierd. i just sold my 8 1/4 to a fabo member after swapping in a b body 8 3/4. they definitely made BBP 7 1/4 rears. ive seen a few. i think mopar did 2 stupid *** things back in the day. start the 4" b.p. and the way they fastened the dash to the car.