I have a 69' Cougar with the standard gauge cluster (Speedo/Fuel/Temp) and I'm thinking of replacing it with the an XR7 cluster (Speedo/Tach/Amp/Oil/Temp/Fuel). Is this going to be a plug and run swap, or will I need to replace the sending units. I believe I have the schematic for wiring the tach. The stock cluster is red, and believe the XR7 cluster I'm pondering is red as well. Any advice would be appreciated.