If you wanted something new to try, RideTech released a FoxBody IRS kit. I've been planning to take some measurements of my rear frame rails to see if maybe it could be adapted to a Duster.
[URL]https://ridetech.com/product/1979-1993-mustang-irs-rear-suspension-system/[/URL]
Not cheap and it looks like you have to buy axles separately, but the overall width should work if I remember correctly as the FoxBody 8.8. is about the same width as a '65-67 B-Body. No idea if the frame rale widths are even similar though.
My budget restricted plan right now for my '73 G3/T56 swap car is to grab an 8.8 out of a Crown Vic since they use a 3" axle tube. I am going to use Moser axle ends 7750K so I can bolt on '05+ Mustang brakes and delete the c-clip as the Moser ends us a press on 9" axle bearing.
Bottom dollar, I will make sure to grab an '05+ CV axle and just narrow the housing and get custom or shortened axles. The '05+ CV 8.8 got 31 spline axles and the brakes are even bigger than a 2010 GT500.
My only real concern with the CV 8.8 is the axle shaft size at the wheel bearing. They are kind of small in my mind. But plenty of people run them without problems so probably just me overthinking things.
Oh and a CV axle will require me to re-gear it as they didn't have many options for gear ratios beyond a 3.55 in the police models and I will probably need something deeper with my T56. Might not be an issue for you though with your 8A.