What is this part and hose outlet and factory A/C questions

[64fleetside]

Originally Posted by chevyrestoguy

When I did the body work and paint on my firewall, I temp-installed the evaporator assembly and then tightened up the feed-thru holes in the firewall by welding in a filler panel that put the holes in the exact spots that they come through. My plan is to use bulkhead grommets to make the evap tubes as air-tight as possible.

I think originally there was a rubber seal on those hoses-I used some rubber to re-create one. Mine works great but it is somewhat noisy compared to newer vehicles-a lot of air comes out that single vent.