Never completely cured it and can't find anything wrong - In fact, because the shocks were shot and the top mounts past their best, I rebuilt most of the front suspension, new top mounts, shocks, springs, in fact everything except the front arms which were in excellent condition - I suspect they'd been replaced shortly before we bought her. The only thing I do think is that the arms are not from the same manufacturer and one is probably a little newer than the other. I've spent hours checking and the only thing I can think is that there's a slight difference between them? The pull to the N/S is very slight and I just live with it.
Replacing bushes or complete arms? without a press it can be a pain. I'd burn the rubber out and carefully cut a slot in the steel sleeve then chase out with a punch or chisel. However I've wasted hours on some vehicles trying to get the bushes out, so, if I'm doing one at home, I'd go for a replacement arm every time unless the arm was a "silly" price. If I had to do bushes I'd be tempted to go with Poly bushes.