Do you have the four seasons heater control valve, or an original? Maybe post a pic of it and we can help. If you’re just using heat, you could manually open the valve under the hood. Problem is you’ll always have hot water flowing through the heater core, which might make it hot during summer.
Where is it cut? From the heater control panel? You could just remove it from the slider that controls temp, and take the screw out of the little plastic flag that connects the cable to the heater control panel. Let me tell ya tho, it’s a pain in the ass to install the cable with the dash in. I’d buy a cable while the dash is out, connect it to the heater control box, and fish it through when you install the dash.