Yep, unfortunately, we may not be able to use the stock sensor as it has very small resistance change between 190* and 220* (only about 10 ohms). In contrast, the GM sensor has 240 ohms difference in that range.

This means if the stock sensor is off by even a little bit, it throws the temperature way off. I got three sensors from the junkyard to test. The two that were closest, were 10 ohms apart from each other. The third was 100 ohms off.

Right now we're looking at using an Autometer sensor that will thread in place of the stock sensor. The controller can still drive the stock gauge in the dash, so I think it will end up working just fine