Hi Jack,
I couldn't really tell if you are attempting to leave the arms on the car or take them down with the axle.
If the intention is to leave most of the stuff on the car, the trailing arms have to come down either way on a wagon.
Remove the forward bushing bolts (at the body) and pry the front of the trailing arms down. On the big rear block bushings, remove the two big lateral bolts and the two smaller bolts under the bushing. Use a flathead screwdriver to pry the block bushing out. Once the bushing is out, you can twist the trailing arm enough to clear the axle brackets.
Of course the lower portion of the shocks and the IPD bar must be freed in addition to the items you mentioned removing.

I've seen a late sedan axle in a wagon once but the owner said she could feel a vibration at speed. There was no welding or cutting at all, whomever performed the conversion just chose one of the two bolts at the block bushing and used that, leaving the other hole on the block un-used. Cool but weird.
It was a '67-'69 drum axle so there were no driveline issues.

A local guy here has the big driveline in his '68 rear-disc 122 sedan w/OD (not Rose City Cameron - different car). The front flange rubs/scrapes the tunnel on light bumps. We plan on doing the short-stick conversion to this car, hopefully we will remember to hammer or cut the sheet metal there to accomodate the big flange before we put it back together:o)

"Now, once it is free, I want to pull the half-shafts to better inspect the bearings. How best to free these guys? They are in very tight and I think some sort of specialized puller may be needed."
Remove backing plates and shims then use slide hammer with a fabbed-up tip that will screw onto the stub end of the shaft; I welded a spare axle nut to the nut that came with my slide.

Don't know anything about adjustable arms for 120's, sorry.

Best,
Shayne.