Any way to get the gc2 image sensor to work on the gc3?

I saw that there is a different image sensor for the gc2 and gc3 from I’m thinking of upgrading to the fc3 but I have 2 image sensors on my current system.

That is correct, the GC2 uses a different image sensor model than other panels. Upgrading to a GC3 would require replacement of the Image Sensors, or at least the existing ones could not be used.

The GC3 Image Sensor can be found here.