Been chasing Death Wobble causes for a little while now. Drilled some steel plate and had it welded to the outside of the trackbar mounts on both exteriors of the axle and frame side (thank you, new girlfriends' Dad!
) seeing as those holes were pretty wrecked. Cleared up a lot of the problem but did not fix it.
So then I took a look at the rod ends on the drag link and tie rod, all rooted, plenty of vertical play in every end. Little disappointed that they need to be replaced, but hey, at least I have something to blame the DW on, better than not knowing!