If there's a wobble, check your ball joints; jack up the front end, and see if the front wheels wobble or have any play (check laterally and vertically). I recently thought I had shot ball joints, due to uneven tire wear, and a wobble at 50-60 mph. Didn't have a "thunk", though, which is an indicator of ball joint wear; mine turned out to be unbalanced tires, as one of the weights had gotten thrown, so a simple pressure check and rotation fixed mine. Hope your's is as simple, and not a ball joint ... I understand they can be a real PITA to replace.
-Alan