When you went from stock 30ish inch tires to the 35's, you went to having something similar to an effective 3.11 gear ratio. If you put 4.11 gears in, that is similar to 3.55s.
Pegasus has a little gear ratio tool and the chart on this website
Differential Gear Ratio Chart - Tire Size to Gear Ratio
That chart is pretty close to what I see going 70 with O/D off and the TC locked. You should play around with those to get a better idea of what the different gears will result in.