If your going to drive it on the street a lot, then I would go with the 3.73's. That is what I have in my stang. I installed them myself as well. It wasn't that hard. I took my time to make sure I got the tooth pattern the way I wanted it. I think at 75-80mph, you'll run about 2.3-2.5K RPM. Expect about a 2 mpg gas drop. That's not a lot compared to the amount of pull you get.
I have no clue what my top end is, but I got mine up to 130mph and I was only sitting at 4K rpm.