Routing a 2AWG cable from the engine bay to the back seat... which path?

I've pulled my back seats out, as well as the 1/3 back panel, leaving the 2/3 panel with the subwoofer in place. I'm going to make a platform and a back panel out of plywood. There are a ton of posts and YT videos about back seat deletion, so I've got plenty of inspiration in that regard.

I plan to install a house battery where the cubby was, and I'm going to run a cable to it from the engine bay. I'm looking at the back wall under the sliding window and I notice that there are a couple sets of what seem to be rectangular-shaped open-air vents with rubber flaps. Probably why it's so loud back there now with the seats and panel removed. I don't know why those vents exist, but I'm wondering if I should exploit them to route the wire under the truck and then up and in, between the cab and the bed.

The way I see it, I have a few options, though I don't know how much space there is for a cable of this size:

• Route the cable down from the engine bay, along the frame rail, and up into the backseat of the cab via those mysterious vent flaps
• Route it through the firewall and then under the door sills into the back seat
• Through the firewall and then under the carpet beneath the driver's seat, and into the back seat

Maybe my search skills are trash, but I can't find anyone who's already talked about this on the forums, or on the internet at large. So I wonder if any of you have any thoughts on how I should go about routing to 2AWG from the engine bay into the back seat.

 

Go from battery, along the firewall to the passenger side, then into one of the giant holes on the passenger side firewall, then under the carpet and to the rear seat.

 

They let air pressure out when you close the last door with all the windows up. They don’t allow the air pressure to briefly spike, rupturing* the ears of people inside.

*not really that bad, but gets the point across.

you can remove them and just seal them up if you wanted. Just remember if you get a new windshield installed to leave your windows cracked so you don’t blow the new seal on the windshield before the sealant has cured.

 

you can also run along the frame rail underneath the body, and there's rubber plugs throughout the body that you can come up into near the rear of the cab. there's also ample space in the sides of the main wiring harness grommets to bring it in at the firewall, and route it along the sill plates.

 

Follow (loom and secure) the fused power wire of the inverter...