My indie mechanic has seen three W126 chassis cars in the last four months with rusted out rear control arms. Not associated with rust anywhere else, just the control arm. You will have to crawl under and take a look.
Cheap tires can go bad in a very short time -- had one last less than six months on the Volvo (wasn't what I thought it was, didn't go back to that tire dealer again).
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!