OK, I'm not sure if soaking in WD-40 helped, but I screwed the nuts back on the cotters partially, and swapped out my plastic mallet for my brass hammer. It took some serious blows, but both the cotters came loose. I then bought a SS 1/2" UNF bolt to screw into the spindle, expecting a serious struggle to extract it, but it slid out easily. Looking at the bushings and the spindle, I would bet money they are fairly new parts. One end of the spindle did not have the larger diameter outer felt ata ll, and the inner felt seemed dry. The other end had both and looked better. I see a little galling on either end of the spindle, but I not so much that I would expect to have so much play in the swingarm. Any thoughts on that?
I suppose I'll play it safe and order all new pieces for a 1975 MK III; I believe I've read that it's not exactly the same as earlier model Commandos, and I wonder if the problem could be that someone installed the wrong parts (even though they seem to fit well enough). What puzzles me is that, with such obvious play in the swingarm (I could grip the rear wheel and feel and see it move a bit when I pushed side to side from the top), I would have expected the bushings/spindle to look a lot worse.
Any shops sell a complete MK3 kit for the bushings/spindle/felts/etc?