H78's? How old are those tires? If they are 30" in diameter you should be turning 2366 rpm at 65. If 29 you turn 2448.

Change your axle to 3.50, and you will turn 2548 with 30s, 2635 with 29s.

3.70s: 2694 or 2786.

Not sure the change will be worth it.

Are you in love with your 3 speed and column shifter?

A change to a NP435 or T18 would retain your current cruise rpm, and give you that granny low for the heavy take off situations. Not sure of all the ratios involved, but they might even be better 3 to 4 than the 3 speed is 2 to 3.

To calculate more variables, or if your tires are different than 29 or 30, different speeds etc:

Novak Conversions - Gearing & Gearing Math for Jeeps