355 to 308 ratio?

[JMBT]

I have 3:70’s with a 10spd, and for my application it sucks! I need 3:90’s to run with my 10 SPD in my application. I run 22.5LP tires. When the motor was new and not too worn out I did ok, but now With the worn out motor, I have to hit hills at 65mph to keep the rpm range above 1500. My climbing speed with proper rpm range is 52 in 9th or 65 in 10th, anything less puts me below 1500. So 3:90’s would have been a better choice for me. I could then run 55-60 get the good fuel economy. And still be in the non-danger zone for rpms.