8 1/4 rear question

I looked going to a 8&1/4" and was unhappy with the gearing choices. And with 8&3/4" I was unhappy with the cost. I bought a 1965 mustang 8" rear for ~$200 that I plan to install this winter. The perch spacing and hub spacing are almost identical to my 1965 Valiant (I think your Duster has the same spacing as my 65 Valiant.). Someone sells and adapter u-joint. (I forget who.) The Ford axle Has the 4.5" bolt-pattern. Has 3.00 gearing. Has 10" drums though... so I am only planning to upgrade once I get the front discs breaks in (I don't want the rear to have bigger brakes than the front). That project should start in a month or something. Going to big-bolt pattern to have more wheel options. Anyway... FWIW, I really haven't started the install so there are probably some unknown unknowns. (Like: do I have to shorten the drive-shaft and what to use for a pinion snubber.) Anyway, the old Mustang rears could be an option for you... if you are not 'anti-Ford';-)