[ERASER5]

Since you live in SC, the heater should be enough. You may have to run the A/C at the same time like defrost to keep the window clear in the winter. Vintage, like most other after market HVAC systems, dose not use outside air at all. This can cause fogging in heat mode. Are you planning to drive it in inclement weather?

No outside air allows you to fill the cowl, fill the vent holes with speakers, fuse panels or what ever you want. Sealing out the air channel also helps control rust.