I finally got around to fixing this thing this morning. The gear I ordered from ODO gears was not the right type. You apparently cannot get the brass gear. So, I got a used speedo/odo from daw_two that has the 15 count brass tooth (for a 2:88 diff.) and that fixed the problem. Obviously at some point the speedo was swapped out with one from a different car with a different diff. ratio.
After a quick ride with the GPS both the speedo and odo are so close to what is indicated, it is not worth worrying about. Now I can check my mileage and figure my oil change intervals with out doing math.
Thanks again for the help Charlie!
If anyone needs a speedo/odo in good shape with the 18 tooth brass gear... Let me know... I have one available.