speedo calibration using abs sensor 95 LT1

[mopar[maniac]]

Hi, im new to the forums and fairly new to tunerpro and so far i really like it as obd1 system. My question is i have the speedo wired to the abs sensor on my 94 z28, originally a m6 car but now has a th350. I need to know how to calibrate the speedo. I know where everything goes but i dont know how to get the values needed. I know you use the rev per mile of the front tires. Thanks in advance, ive read till my eyes bleed and cant find the answer lol