always a good idea to take a picture with a digital camera of your needle positions before doing any cluster work.
anyhow, take your gauge cluster lens off, start your car and let it warm up for about 10 minutes, once it is completely warmed up center all your gauges except for your speed, tach, and fuel.
oil pressure - center
battery - center
engine temp - center
now shut the car off but leave the key in it, hold the trip reset button in now turn the car to accessory, continue to hold the trip reset button in until the word TEST appear. now start your car. using the instructions from the link below, hit the trip reset button until you get to RPM's. take your RPM needle off, and while the car is at idle, match it up to what is being displayed on the digital readout. doesn't have to be perfect just get it as close as possible. when you have matched as close as possible gently push in until the needle is halfway in (DO NOT PUSH IT IN ALL THE WAY, IT NEEDS TO BE FREE TO SWEEP LEFT OR RIGHT). now shut the car off to ensure the rpm needle is able to sweep. once it's good, turn the car off, turn the key to ACC and repeat the process to bring the diagnostics back up.
this time you're gonna hit the button until you get to the speed display. this is a little tricky, but get on the interstate and set your cruise to about 65 or 70 mph according to the digital readout. Keeping one hand on the wheel, use your other hand to get the needle into position, and once you have it, gently push it in halfway. you might be a mile or two off, but that's ok...just don't want to be anymore than that.
Now go to a gas station, and top your tank off to full, start the car, and place the needle just barely to the right of the full mark. check all your gauges, you should be good to go now, again push it only in halfway to ensure the needle will sweep. turn the car off, then back on again, to ensure all needles sweep to their appropriate position. put the lens back on, and you're finished.
http://www.mustangworld.com/ourpics/fcar/dtcodes.htm