A quick question. I am preparing to replace my heater control cables on my '55 Bel Air. Do/will I need to unhook the heater hoses under the hood, drain the heater of fluid and completely remove the heater in order to change these out or can the cables be exchanged with the heater in place. Annother possibility is, can the cables be changed out by leaving the [under hood] heater hoses hooked up and remove the heater housing. Just want to know ahead of time before I start the process. Thanks to anyone that can help me out.