Gear Selection

I have decided to go with the 3.55's. After doing some comparative research, it will be fine. My dads all original '70 T/A has a 4 speed with 3.91's and G-60 tires which is about 26". So at 60 his car is running about 3100 RPM. My car at 70 will be at 3200 RPM with the 3.55's. He also had a '69 Dart that had a 340 3 speed A/T with 4.11's and F-60's or about 24", 60 MPH = 3400 RPM. He ran his on the interstate a lot back then.