Speedo Calibration Question
 

i have an 88 GT and i bought a new instrument cluster (white guages and a 200mph speedo) and the old 90mph speedo was calibrated differently obviosly..... how wud i go about doing this
#1: Getting the speedo recalibrated (if it needs to be)
#2: getting the odometer to read the correct number of miles the car really has

i need help w/ this please reply...thanks