I hoping no news is good news. I checked my 'inner' axle, and it has a rubber-like/paper coating - almost like a tar paper around the axle. I was cleaning the 'external channel' of the axle - I initially thought it was just dirt - but it appeared to be an undercoating of some sort.
Were you able to find lower spring isolators? I think I saw some at Rock Auto, but I opted for ones from PolyBushings - the set of 2 was approx $25 delivered. Mine appeared 'intact' but felt 'crunchy' when flexed. Uppers had 'spring indentations' but appeared/felt OK - I didn't replace them.
So far so good. I've driven over 1,000 miles with the foam stuffed into the axle, and all is quiet, the ride is fine. I did install newer lower spring isolators that I bought at Rockauto, and they work fine. Dakota Dan sold me the axle and also had the jounce bumpers, which had rotted off mine. I installed the left one fine, but one of the two bolts on the right side broke, so I left the stub of the old one there. Next year I'll drop the axle down,remove the spring, drill out the bolts and install the new jounce bumper with a bolt, nut and lockwasher.
So in Sep 2013, I filled an area the size of my fist on either end of the bar with Great Stuff insulating spray foam, and it held - for 18 months and 20K miles. Now it's starting to rattle again, probably the foam finally shrank some. I'm going to shoot some Liquid Nails in between the foam and the bar to secure it in place.
I had a broken rear sway bar tube in my 1986 LeBaron convertible and I wanted the rear disc brakes from the 1989 LeBaron Coupe I was scrapping ($50 no title parts car). I found after I got all the suspension parts off it that the rear sway bar tube was broken at one end. I went to Pick-n-Pull in Virginia Beach and pulled the rear axle from under a 1995 convertible. I found a number of small differences (a) pivots, 1986 has smaller bolts than either 1989 or 1995 (b) bushings, in addition to larger pivot bolts the bushing are longer for 1995, same OD, just longer (c) brakes, 1986 had little teeny rear drums, 1989 had the rear discs with internal drum parking brakes. 1995 had larger drums (d) front mounts, 1986 have small pivot and slightly angled parking brake cables, 1989 has large pivots and straight parking brake cables, 1995 same, but the brackets are wider.
I ended up buying the 1995 axle as it was the only K style in the yard. I pulled the rear brakes and spindles and left them in the car on the appropriate side rear floor. I used the 1989 spindles and hubs, cleaned repacked and new seals then installed new parking brake shoes and return springs. Since the car isn't on the road yet, I can't say how it drives, but moving it around the garage they feel great. I did transfer the master cylinder, booster and equalizer block from the 1989 car.