Gear Ratio and RPM deciding on gears

I have a 340 runs pump gas and my power band is 700 rpm higher than your chart. My car is stock 3.53 and I can cruse 70 in it but not 80. I wouldn’t recommend 4.11 on the freeway for any distance.
Yeah the power band is a guess and every set up different. What kind of rpm are you at 70mph?