cutting back of dash

Are you sure that the proper hookup isn't there already?? The hole should be the same between the light and the guage, and it must have a 2 post system that is run through the circuit board! I don't think the circuit board would change unless it's not the same year guage and car! The change would be in the sending unit, which sends a signal to either the guage or the light, with a different sending unit for each option!! Correct me if I'm wrong, but I think that's the way they're coordinated!!