[Submariner616]

Originally Posted by SkinnyG

https://www.vintageair.com/instructions_pdf/751163.pdf

Instructions show plate to cover it. It -looks- like the original opening is going to be reasonably blocked by the evaporator unit.

My question wasn't about losing the floor vents, but not putting fresh air through the heater. I have a V8 Pontiac Firefly (Chevy Sprint) that I built that has a fan on a heater core (no fresh air to heater core, just cabin air) and it sucks for defrost.

In Defrost mode, the air conditioner is on and is dehumidifying the air, which helps defrost, just like modern vehicles. Reducing the humidity in the cab helps all the windows stay clear.