Difference between 3:55 and 3:23 gears

Wallace Racing Calculators has some great tools to help you with this.
I have the 3.55's with 245/60-15's and the TQ904.
Puts me about 3150 rpm @ 70 mph.
You can find them here.
http://wallaceracing.com/Calculators.htm
This one helps a lot with MPH GEAR RPM info.
http://wallaceracing.com/calc-gear-tire-rpm-mph.php