Can anyone tell me if there is a company that can recalibrate and reface a factory tach and speedo to read a higher limit from a 1987 grand prix?  

if you have a kph scale on you speedo head you can get at any speedo shop a converter box that screws on next to the tranny that allows the kph scale to be accurate in mph... that is the easy way to do it..... and it will take longer to jack up the car than it will to install the cable ratio box......


i dont know what it is going to do to the ecm calibrations..as there should be a speedo pick up the back of the speedo head that counts the turns of the speedo disc optically so the ecm knows when to lock the torque converter...

you should also measure the roll out of the rear tires so it can be included into the ratio conversion to bring the speedo back into true miles per hour...  

I want to change the 80 mph speedo to read 140 or 160 mph and change the tach to read 8000 or 10,000 rpm.