How do I seal off the fresh air/ heater intake?

Best way to do it? Is the factory climate box setup for recirculate, or will I need to cut a hole in it?

Before anyone tries to tell me that I should find the cause of the smoke coming into the cab, don't. New weather stripping, sealed up the cowl, siliconed every last inch of every gasket in the engine, and still I'm breathing in smoke. It is time to seal that f*cking vent.

fresh air door on passenger side A pillar is an area to close off. The heater box gets fresh air from the same area, the pocket down the side of the windshield trough

Once I seal it off will I need to cut a hole in the heater box to let it suck air from the interior?

It won't work that way, only the blowing side of the fan is hooked to the hot/cold mix door into the bacin.

You could remove the whole heater box and blank it off and put some kind of blower in the interior. Spal makes some nice compact ones.

Vintage air GenII heater... Compact, and moves some serious heat. electronic servos and heater hose valve. Draws air from inside the cabin

Lightening storm, off the air for about 24 hours here, even blew the HDMI input to my TV......

as to your door, you need cut/remove the right side wheel liner, I just put in a piece of vinyl in it's place....screwed to the glass, this enables getting to the blower motor FAR easier, once you remove IT, you can see and get to the door that is in the chase area TT refers to....that can be unbolted from the WSW area, and dropped out, disabled on the spring action holding it open, so you can use RTV to seal it closed like I did years ago, then removing the door on the right kickpanel inside, and tossing it....obviously plugging the vac hose controlling that function, this puts the HVAC system on permanent recirculation.....mine this way for many years...

:crutches: