Most of my vehicles without OD run a little under 3K going down the freeway (closer to 70 though). If I were me, I'd look for 23-2600. Lower might give you a bit better gas mileage but may not have the power you want to accelerate a bit without downshifting.
My 59 Suburban has a 350, 3.40 gears and 31x10.5-15 tires and cruises nicely at 60, 70, or faster if needed. You will probably want taller tires than that with your 3.73 rear gears.
