Passing a power cable through the firewall on a 24 1500 - Very different than 2019-2023 models; seeking advice

[DubVBenz]

I have a 2024 GMC 1500 and I wanted to wire up a subwoofer behind the rear seats. I found great guidance on various forum posts and youtube that showed a unused grommet through the firewall that is intended for aftermarket cable routing (power/subwoofer or otherwise). It had a closed rubber nipple that you could cut off and fish a wire through there to the passenger side footwell.

 

So today I began the process to fish a power cable through my truck's firewall and found that it's completely different. There is no longer a passthrough grommet. I took out the battery (with much frustration ) and couldn't find a single place that I could see to get something through. I found a post online that I cannot seem to find again that stated the 2024s were completely different, and based off that description I think it's accurate. 

 

So does anyone have any guidance they can provide to get through the firewall without drilling? Looked very simple on videos for the 2019-2023s.

[DubVBenz]

Here's the one thread I previously found, on trailboss, so replace the URL because the **** mods apparently don't like competition. www.notrailboss.org/threads/firewall-grommet-change-in-the-2024-lt-trail-boss-for-power-wire.2109/

[dieselfan1]

There is a opening below the battery on the firewall. Looks like a plastic tube. It comes out below the lower glove box.