It is a very straightforward process to attain this goal. First, remove the instrument cluster and disassemble the gauge. Next create a schematic for the gauge, from visual inspection and from x-ray images, for the hidden traces. Then download the firmware and reverse compile the code. Don't forget to add comments to aid in reading the code.
Once this has been completed, changing the code, to attain your goal will be easy.
Please post the results.
2001 GT-S 6-speed
no side air bag
ALL other options