I'm running around 4000 rpms at 70mph. Haven't had the car dyno'd yet but it'll run mid 11's or so on slicks. Unfortunately I didn't get too much info on what the previous owner had done to it as he passed away and his grandson sold it. I'm thinking 3.55 might be the way to go. Worse comes to worse I can move up to the 3.73 I guess.