70 duster 8 3/4 conversion to 4.5 drum or disk hardware

Jimacuda, is right. I just did this on a 8 3/4. The backing plates are 10 1/2'' B body. all the shoes(2 1/2''),hardware,and drums are from a 80's Dodge Diplomat.
You can use the Diplomat backing plates, though some only have a 4 bolt attachment and you can drill the 5th hole to bolt to your axle housing.