Well if you dont have a gear in there now youll pick up something in the 1/4 but if you do dont expect anything.I went from a 3.55 to a 410 and never picked up anything except a blown piston from hitting the rev. limtr. All you do is shift quicker unless your the absolute best of shifters.Max speed in 4th with a 410 and 6000 rpms 112mph,390 and 6000rpms 117mph,373 and 6000rpms around 123mph.But if you drive freeway goe with the 373s I just had them put in by Venom99 and they pull around 2500rpms at 80mph in 5th.