car rides horrible at highway speed... what would i need to check... can it be warped rotors? it seems to shake and than go away and than shake i got no clue.. its going to need an alignment soon... mechanic said 55 to do that sound good?

Alignment and wheel balance are a place to start.

Just remember, the Mark VIII needs a 4 wheel alignment, not just front end.

Could also be sway bar end links. Mine were bad and the car shook like a S.O.B. at 45 mph plus.