Syncing my iPhone 3GS with 2010 Ford Fusion via bluetooth
First, turn on Bluetooth in your iPhone: Settings>General>Bluetooth
Second, leave this Bluetooth setting window open
Third, start the process in the car as you have done before to get the 6 digit SYNC number
Fourth, enter this 6 digit number into the iPhone Bluetooth settings window (NOT the phone keypad). Do it quickly as this number is time limited and if you're slow you'll have to start over.
Once your are SYNCed, the iPhone Bluetooth window will show SYNC and will remember this connection.
The SYNC feature works great with the phone and the iPod. You do not need a bluetooth headset. The whole point of the Ford SYNC feature is to use the car audio system for your in car phone calls.