Question on 1989 K5 driver side HVAC tube reinstall

[Clark75K5]

This was out when I got the truck. Got a new dash pad and want to get all this stuff buttoned up.

What is the preferred way of installing this? Do I need to remove the deflector box that bolts to the inner heater box?

Also would be helpful to know where this bolts to.

Here is a link to an aftermarket one for reference.
https://www.usa1interiors.com/1973-87-fullsize-chevy-and-gmc-truck-hard-plastic-air-duct-left.html

 

[frankin5]

I put mine in the plenum first and then slip it over the round plastic of the dash out on drivers side. There is a screw mount under thr steering column. There are no screws on either end.

 

[Clark75K5]

Can you do this with the plenum still attached to the heater box, or remove the plenum first? I guess I assumed there was a flexible duct needed to attach to the vent but if it just goes directly into the vent, this leaves out a lot of guess work.

 

[Clark75K5]

I got it all figured out, thanks for your help. Looks like I need to order a new LH Heat/AC outlet.