18x8.5 +30 offset all around on 72 duster?

You can also run a 68-70 B-body rear end and move the spring saddles in 1/2" on both sides. That would also get you a rear 1.5" wider on both sides. Much cheaper that large bolt A-body rears.

Would be good idea since you are moving spring saddles at that point, to move the spring 1/2" more inwards with a bolt on A-Body Offset Spring Hanger/Shackle Kit: Mopar A-Body 1/2" Spring Relocation Kit Offset Hangers & Shackles

Rear end widths, drum-to-drum:

A BODY
'66-'72= 57 1/8"

B BODY
'62-'63= 58 1/2" (And '64 Max Wedge)
'64 = 60 7/8" (Exc.Max Wedge)
'65-'67= 59 1/2"
'68-'70= 60 1/8"
'71-'74= 63"
'71-'73 wagon= 64 3/8"


Spring perch widths (center-to-center)

A BODY
'66-73= 43"

B BODY
'62-'70= 44"
'71-'74= 47.3"

C BODY
'65-'73= 46"

E BODY
'70-'74= 46"