I purchased a new 70 road lamp switch from year one. There is a 3 wire harness on the switch. Is 1971 also a 3 wire or whats the differance between the two switches. I see they sell 70 or 71 switches with different part numbers. Reason im asking is im having a issue finding the plug under the dash to connect it to. And not knowing the car since 1970 maybe it has a 71 ralley dash/harness or dash since then. THANKS