Leroy, if that is the smaller sized speedo gear that GM used (and it should be) they came in sizes from 17T up to 24T. I usually found that each tooth made a difference of about 5 mph. When you are figuring out how many more or less teeth you need, don't forget that this is the DRIVEN gear, not the drive gear for the speedo cable. I can get you GM part numbers or source out the gears for you once you find out what you need.
