Interior HVAC grommet ID Help

[71RT383]

     Somewhere along the way, my HVAC interior grommet (2 hole) went MIA.  I bought a replacement.
My understanding is the HVAC (small diameter) vacuum hose runs through the smaller grommet hole connecting to the rear manifold vacuum tee. 
Not sure what runs through the larger hole as, my Heater Control Cable has the long grommet attached and exits via the drivers side firewall. 
Is there another hose or line that I am not accounting for?  Or were they plugged if not used?
    I do not have any helpful photos of it. Tried the manuals to no avail, possibly overlooked during search.
  Thank you in advance for any and all help.

[headejm]

@71RT383  Here are a couple of photos from my 1970 Challenger R/T SE 383 w/ AC. On mine, there is only one vacuum hose that passes through the grommet and connects to the vacuum fitting in the back of the intake manifold. I didn't have to plug the other hole in the grommet. It was already plugged from the factory. 

[71RT383]

    Thanks for the pictures and info, headejm. I will plug the other hole and I'm good to go.
    If only all repairs could be this easy!

[R/T's 4 R/P]

My car came with AC.  Like many, the car had all/most of the AC stuff removed over the years, so I needed to buy and/or research all the pieces.
When I got my car, the cable for the water valve from the dash ran through a hole in the dash by the left side hood hinge.  The hole the cable ran through was actually a hole for a sound-proofing panel 'nail'. Not sure who did that, or when.
I also needed to get one of those rubber, firewall grommets, as shown in your photo.
Well, lo and behold, i discovered after looking at a few non-molested original cars, the cable actually runs through one of the small holes in that grommet.
So, the water valve cable runs under the dash, from the control panel, through that grommet and up to the water valve.
I believe this is a 1970 routing only.

[anlauto]

You're correct...at one point in production the cable also ran through that grommet 

[71RT383]

 

[headejm]

Since (at least) 1980, my temperature control cable exited the firewall behind the brake booster. My firewall grommet only has one through-hole it it for the vacuum line. Since I don't believe my grommet was ever changed, it appears that my temperature control cable never exited through the grommet. SPD 508.