Reply to "Axle problem?"

FWIW, I've never seen the splined end of the stub axles wear enough to see movementunless the retaining nut is loose. Incidently, the nut takes a special pin-spanner-wrench to tighten or loosen properly, and your axle may be right or left-hand thread.
There is sometimes a little play in the spider gears inside the differential, or in the inboard stub-axle where it splines into the side gear. Another place is the lower cross-shaft thrugh the lower a-arm & carrier. At that point, there are a pair of thin-wall bronze bushings that likely have not been greased since the car was built in Italy, since one must disassemble the a-arm from the carrier & hand-grease this area.
Finally, although I doubt anyone is strong enough to detect it by hand, the outer stub axle often wears against its bearings, to produce a deep 'wagon-track' in the axle surface. Under power, this acxtually changes rear wheel alignment & accelerates tire wear.
All this stuff requires an experienced eye to determine what if anything should be done. There are the normal Pantera parts vendors scattered across the country that could inspect this condition. Long-distance trouble-shooting is tricky & often unsuccessful.