thanks for the replies. i may just throw the 3.31s on for now, and if its not enough the 3.73s later. but with that an after market tune will be needed or would ford due the tune because it would just be gears that you can get on their web site.
I'd just get the gears you want and get it knocked out the first time around. It will save you several hundred dollars in labor, that is if you're having someone install them for you. You could even have another shop install the 3.31s for you and have a Ford Dealership flash it for you. I know I was quoted over 1k for a gear installation at a dealership, I had a well known performance shop quote me for several hundred less.