Cables can be run along the passenger side of the car and if you lift up the carpet you can see how much space there is in there in and around the factory harness/ power cable (which i found odd that it is actually welding cable being used).
Gotcha - so I can just snake it along the existing power cables. Ah, I actually hadn't thought of that right away - the battery cables have to run from the trunk to the engine bay already - makes lots of sense.
Thanks for knocking my brain in to gear. That's exactly what I needed!