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temp sensor and temp gauge output

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I'm still in the planning stage and spending alot of time in the schematics for the car.   The factory ECU used a water temp sensor, and the factory dash used a separate temp sensor for the the water temp gauge.   I found that the water temp shares an isolated ground with the oil pressure sensor as well as an outside air temp sensor all of which have an associated gauge or digital read out.    My plan was to use one water temp sensor for the Link Thunder ECU and just run an output to the dash for the gauge.   What is the collective thought on this?

The car is a 1990 Porsche 928.   The factory  ecu used a Bosch temp sensor & the dash water temp sensor is a VDO sensor.   I was hoping to consolidate to one sensor due to an ITB installation and not having room for the 2nd sensor.

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While not impossible to make a PWM output drive a temp gauge, it will potentially be a heap of messing around to make it work.  You will need to rig up either a resistance substitution to fool the ECU into seeing different known temps, while adjusting the PWM to make the gauge reading match, or use something like a hot pot of oil heated to different temps while you calibrate the gauge.  The recommended option would be to have separate sensors.

If you had to use a PWM output, the wiring would be temp gauge signal wire direct to aux 1-8, and the gauge ground wire I would connect to chassis ground rather than the ECU sensor ground.

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