There should be two grounds in the headlight wiring harness. They attach to the front of the radiator support. One on each side. There is only one wire that needs to be swapped around from the std inst connector to the stacked. I can't recall if it's the temp or the OP. I have no idea about the rallys gauges. The shop manual has an illustration of the inst connector. If you don't have the book, get one. You'll use it alot.
