I just ordered my Torsen today for 534+ shipping. It was the last one listed in the Ford dealership's database.
If anyone is still looking ford has posted that their estimated delivery date is April 6.
Best places to find them for under 550 are:
1-800-328-9552 ask for Steve 515+ shipping
JohnBleakleyFord.com
McNewsAutomotive.com
wakeperformance.com
(704) 938 3121 NC Ford Dealership ask for Sam 534+shipping
And this guy on Ebay still has them:
Bryant Motorsports