looking at getting a set of 4.10's for my 01 cobra.. my question to you guys is about the calibration of the speedometer.. i know they make the diablo and other tuners.. do i need to purcahse one of those in order to recalibrate the speedometer or is there something cheaper to do this? i know the tuners will get me more horsepower but money wise im not ready to buy a tuner yet.. any input would be appreciated.. also the mechanic said 390 to do the job, seems pretty fair to me... thanks..