Under dash mystery holes....?

Was under the dash working. Looking up on each side in the cross frame area mad also what I believe to be the passenger side defrost. There are 4 total holes maybe 2.5" diameter . 2 in the frame, 2 in the fiberglass. What are these used for? Does hot air channel up through the frame somehow ? Thanks.

Yup - look in build manual in Library and you'll see the install of the optional foot heater slides and the dash defroster vents. Of course you'll need heater boxes on the engine connected. Probably a lot of heat loss as it is not insulated in the chassis. DrClock runs his down the center tunnel as an alternative.

Yeah my foot heat works really nice actually.... Cool thanks!!!

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I'm going to get some foil hose and try. It. We had some defrost issues, this might be enough to fix it or help at least.

You'll need the foot slide valves so you can close off or partially close off the floor vents (Ok I see them in your photos) and direct heat up to the defrost vents.

I already have the foot control sliders and they are in place... My floor heat works pretty good ! Sounds like I just need to route the defrost and I am good... Not sure how I can attach the hoses to the holes. Maybe have to epoxy some PVC 2" or something to make it work.

If your holes are the right size you could use the OEM rubber/steel grommets that are used to pass air from the doghouse and through the engine tin, no?
If they'd work they'd provide easy attachment of your defrost hosing.