I'm outta whack!
 

Just had the tires rotated/balanced on my 1985 500SEC/AMG today, due to wobble over 50mph. However, after the balancing, I still have the wobble above
50mph! Ugh, it thought this would take care of the problem. Anybody have
ideas as to what I should check next? Thanks!

Bet you have a bad tire. Swap the tires from front to rear and see if the problem follows.

wobble down the road.
 

could be a bent wheel. Happens a lot to alloy ones fitted with low profile tires. Check the run-out