I had wanted a way to display an AFR gauge in the car without adding extra gauges and so I set about making this, utilizing the stock clock location and control stalk. It's not such an easy install into an S15 as it requires cutting and drilling to the gauge cluster and destroying the original clock but it looks pretty good IMHO.
ESP32 Arduino CAN BUS Multi-gauge / S15 Silvia - YouTube
ESP32 Arduino CAN BUS Multi-gauge / S15 Silvia - YouTube