MUCH progress to report today. My brother came down again and we got the following done on the Duster:
(1) Finished the rear axle install. Filled it with gear lube and the correct friction modifier for the sure grip, verified all bolts torqued properly, switched the shock plates around so they were mounted properly (D'OH!).
(2) Checked the transmisison fluid level and checked for leaks. Last year this transmisison decided to puke all over the floor in my garage. I thought it was the selector shaft seal, but when I got under the car to inspect it today the selector was bone dry. We wiped the trans clean, topped it off, ran the engine, and are going to let it sit overnight and see if we can find the leaks. In the meantime, the rebuilt transmission is doing great!
(3) replaced the leaked power steering pump. The engine and K-frame are just covered in about an inch of crud from a leaky power steering pump. I was going to put on a used power steering pump I got from Zorg, but I discovered that the power steering pump on the Duster is an older style, not the mid-70s style I got from Zorg. I ended up installing a power steering pump off of a 64 Dart that Midi gave me years ago. Leak fixed!
(4) Brakes bled all the way around and work good now.
So that means the Duster has new brakes on all corners (discs up front, 11 inch drums out back), a rebuilt front suspension (HD rubber, not poly), a rebuilt transmission (wide gear ratio with V-8 guts otherwise and a shift kit), a 3.21 gear ratio 8 1/4 sure grip rear axle, factory HD six leaf rear leaf springs, and new HD rubber bushings in the rear suspension. Mechanically, it is just about done. Time to start getting serious about finishing up the bodywork. Time to strip it down, sand it, and paint it. Cleaning the engine and engine bay is going to be a real chore. The K frame is so dirty I am tempted to just buy another one.
My brother was so excited about the progress of the Duster that he had to take it for a test drive. This is the first time he has ever driven his Duster, even though we bought it back in 2009. Time flies! The downside is that the seats in the DUster aren't bolted down yet and he accidentally leaned back in his seat and broke the replacement windshield I was storing in the car (to keep it safe from being broken

).

So now I am looking for a replacement tinted windshield again.
Here is video of my brother's first time driving his Duster:
Driving away
Returning
The scraping noise you hear in the second video is the front right turn signal bulb dragging on the ground. No noise from the rear axle, transmission works great, no problem getting up my steep driveway, and the brakes work good except my brother says you can tell they are manual brakes.
Pretty good days work. It is nice to have this project moving forward. I also ordered a full set of new KYB shocks for the Duster.
This might truly be the year this car gets done and back on the road!