I'm surprised that no one has mentioned that your choice of gearing is way too low.

My car has a 4L56E trans with same overdrive ratio as a 700R4. I chose 3.50 gears, even with large 30.5 inch diameters. That ratio is none too high. The cruising rpm at any given speed is higher than my 2014 Corvette.

When making calculations for performance, treat the trans as a 3 speed, since the overdrive 4th is only intended for highway cruising. My car has a theoretical top speed of 155-160, if the wind resistance is not excessive. That's in third gear, not 4th. The lowest gear is still far lower that I need for a car that's under 3000 lbs.

Cars like the new Corvette don't hit their top speed in the tallest gear either. It's simply there to increase gas mileage on the highway. You may see a modern car shifting into that tallest gear at a relatively low speed and running as low as 1200 rpm. It will only downshift if you give it some throttle for quick acceleration.