Info on 7.25 to 8.75 backing plate swap

Here are some on the evil bay.
http://cgi.ebay.com/ebaymotors/70-74-Mopar-8-3-4-Rear-Brake-Backing-Plates_W0QQcmdZViewItemQQcategoryZ34199QQihZ013QQitemZ230228527837QQrdZ1QQsspagenameZWDVW
Edit: I am not 100% sure if these are the exact right size. I thought the originals were only 10" this is all I could find:

A-body 8-3/4" axles were equipped with 10x1-3/4" drum brakes.