speedometer gauge off

when i bought my 87 5.0 it had the 160 mph gauge in it. i just got 3.73 put in the rear and i bought the speedometer gear for the 3.73's from steeda. but the speedometer is still off. thought about getting it recal'd but the speedometer was fine before. any ideas?
 
How much off is it? If it is only a few miles, that is probably as close as you can get without getting a universal ratio adapter box for the speedo cable. Which gear did you get, the 21 tooth gear? That is what I have in my 87 with 3.73 gears and it is about 4-5 mph fast at 60. If it is off more than that, what tranny do you have? Is it possible you have a newer tranny with the 8 tooth drive gear instead of the 7 tooth one in the 87 trannys? That will cause it to read off a good bit.