i am thinking of changing my 3:23 to 3:73. Can i have a chip burned to the 3:73s , instead of changing out my speedo gears. Thanks

While it's possible to alter the road speed constant and instrument panel constant, you won't get the "Fine tune" ability in the 1991 ECM code enough to keep everything as accurate as just changing the speedo gears. So can you? Yes. Will it be accurate? No.

Get the gears and dive under the car and install them.

I switched from 3.23 to 3.73 gears back in '97 but never bothered to switch the speedo gear until last week. It is too easy not to do.

http://sethirdgen.org/vss.htm

This link shows a step-by-step install with pictures and even has the part numbers of the speedo gears needed for the 3.73 gears. If I remember correctly, each gear was about $7. Good luck with your swap. You'll love the 3.73's.