I think if you do a search on here you will find that the F body rear can work in your Duster. It's not a direct fit, you have to move the spring perches.
C
It is in fact, close enough that you can pry the leaf springs out and bolt it in. Of course, that is nowhere close to correct, but it illustrates that the perches are not too far off.
I have an F-Body rear in my Cuda. Moved the perches in and got about 5-1/2 inches of back spacing and it's good to go. If you have a narrower rear tire than I do (10") a little less back spacing will work fine.