I'd actually go with either the 2.4L or a 4.0L, not the 2.5L. The low end torque is nice but since you're going to be spending most of your time at 65-75mph the other two are better. Mine gets pretty unstable if I start going much over 65mph, and the engine is really screaming at that speed. Exactly because of the 2.4's ability to easily rev higher, I'd suggest it for this application. Later Jeeps even have that 6-speed tranny.
As a matter of fact, you can do even better if you were to get a 4wd Cherokee or Liberty. They have 4 doors and are built to go faster.