I think you nailed it. One thing I have never liked about the Dusters is how the rear tires tuck in so far (been my goal to get them close to even front to back) and it looks like you did just that.
The B body rear really helped with that, unless you really go crazy in the back like I did you can use the same offset front and rear. You could run 18x9's or 9.5's with 275s all around and pretty much be square with the 68-70 B-body 8 3/4.
Hopefully I'll have another update on here soon. I didn't put it on this thread because I had the "lash cap" thread going, but my Harland Sharp rockers were pretty much wiped out. Pretty sure that was a combination of having valve springs that were too light and running the lash caps, the guy that did my heads said they'd work and unfortunately I just believed him instead of double checking everything myself. First big engine build I've done myself and I've definitely learned a couple things the hard way.
I pulled the heads and had them cut for double springs and new seals, so that part is fixed and I've got the heads back on. Now I just need to set up the Crane ductile rockers and get it back on the road. I'll probably need a new set of pushrods, I still need to measure for those but that should be it.