Sounds like the timing chain might have slipped. My Thunderbird did almost the exact same thing--I was on the highway, it began misfiring and losing a lot of power, then it died and wouldn't restart. The timing belt had slipped, and shredded several teeth until the cam timing was so far off that it wouldn't run.
Does it sound any different when you crank the engine? In my case it cranked faster and more quietly than usual, since the valves were open on the compression stroke.
