Speedo Problem

[wxman1]

Bought this truck last summer and speedo
has been off ever since. It read 60 mph when
I'm was actually doing 49 mph. I changed
speedometer driven gears. Went from a red to
a gray. I think thats 21 to 22 teeth. More teeth
speedometer cable spins slower...speed reads lower.
Speedo is still reading 7 mph too high. The Chevy dealer
tells me that they don't make a 23 tooth driven gear. He says
that the only choice at this point is to change the driving
gear in the tailshaft. I never done that so I'm reluctant to
attempt it.

So other that spending $280 on a programmable
speedo+sender from Auto Meter, are there any other
otions?

Jim M.
Mt Juliet, TN