Where are you located?
I would suggest an appropriate sized linear potentiometer probably mounted on the shifter end (but could be mounted on the other end of the cable -- it's just usually that is hotter/dirtier and it would live longer in the cockpit).
You wire the potentiometer to one of the analog voltage inputs on the C125, and configure the input for the channel "Gear Pos Volts", load the calibration "Dash Internal Battery Voltage".
You will use this channel to define the position of the shift lever using "Calculation->Gear Detection" menu. Select Method "Sensor", Make the output channel be "Driver Gear Lever" and the input channel "Gear Pos Volts"
Calibrate the sensor by moving the lever to each position (Starting with Park) and clicking the read value button.
Now, to turn the "Driver Gear Lever" position into a "PRND" Gear you will use a 2D table (menu: "Calculations->Tables...") The input will be "Driver Gear Lever", and the output channel will be "Gear".
Set up the table with the first column containing the position values you read in the gear calibration, the second column will contain the output gear. Here's the magic : For the Gear channel: Park ==-4, Reverse = -1, Neutral = 0, Drive = -5, and 1-9 will be gear numbers. Your table might look like this:
0.0 -4 (so the first position is Park)
1.0 -1 (Reverse)
2.0 0 (Neutral)
3.0 -5 (Drive)
4.0 2 (2)
5.0 1 (1)
Then configure the display to use the Gear channel. Whenever it see's Gear = -4, it will display "P" and "R" for -1, etc.
If you need help picking a potentiometer, please give us a call.
David Ferguson
Veracity Racing Data
Paso Robles, California, USA
http://veracitydata.com