I get nervous when I even rotate tires. I've found with heavier cars that each tire (especially performance tires) develop a "personality". When anything changes, such as rotation, new wheels etc, expect a different response.
Might have to bite the bullet and go for new tires..at least for the front.
'85 380 SL (sold)
'85 Carrera Flatnose
'71 280 SL Signal Red/Cognac