I think you'll be fine with your set up. On I-70, without a diesel, I think you have to keep your momentum up and look for safe opportunities to get around the big rigs as the climbs approach. Those being the Gennesee area which is just west of Denver as you hit the foothills. The Georgetown area has a nice steep grade on the west end. Also just before the Eisenhower tunnel it gets steep and then Fremont pass (91) up to Leadville has some nice grades.
Years ago when I towed with a dodge 5.9, 3.92 gears, I'd try to do my towing in the mornings and sometimes chart my course up the river valleys instead of hitting I-70. That truck would climb these passes in 2nd gear, sometimes dropping to 1st and I'd be lucky to hit 25-30 mph. You could hit 50 west out of Pueblo to 285 to 24 and on up to Leadville. Alot longer trip but less strenuous. Love the Arkansas river valley and Salida area which you'd pass through going this way. Like everyone has said, new fluids and good tires and you will be good to go on any route you choose.