The Feather Duster/Dart Lites with manual trannies came with 2.93/4 rears, and a fair amount of 1975-1976 Duster 360's got the 2.94 8 1/4" rear as a 'base' option (most opted for those 3.23's or 3.55's).

But they are a drop in the bucket compared to the tens of thousands made as the A904/2.76 A-body standard off the shelf combo.

As a side note, my 1974 Duster with the stock engine ended up with a few ratio swaps...the 3.21 8 1/4" rear ended up with a bearing problem so I had to swap it out (it was good off the line, and light to light, but it 'whined' in the rpm band about 65mph...sounded better at 55 mph)...
I swapped in 2.94's and it was a little slower off the line, but it liked running at 70 mph, and would be at high cruise revs about 75...
That 7 1/4" tanked so I had a 2.76 rear laying around and swapped that in...it was a dog off the line with the heavy car, it moved fine after about 10 mph on the speedo, and loved to cruise at about 75-85 mph...

Gas mileage was the same highway wise for 2.76, and 2.94...

-D.Idiot