I would skip the 3.55's, they won't be worth it and you won't feel any real gain. Don't look past 3.73's even for hiway driving. I saw another post on here that with 4.10's at 75mph he was only turning 2750rpm. 3.73's will be even lower than that, which I think is very tolerable for hiway driving.
For your speedo you will either need to get a Speedcal ($150) or a custom chip ($250).
For your speedo you will either need to get a Speedcal ($150) or a custom chip ($250).