If taking the battery and tray out really makes it that much easier than there must be another grommet lower down because I can't see that making a difference with this one, there is plenty of access from the engine side, just not from the cab. I'll take the battery out today and see if I can find another one.
I'll show you a pic of the round thing that's blocking me from lifting the insulation higher when I get home.
"back in the floor on your back twisted up like a pretzel" I think this is the part that's getting me.

 

I WAS WRONG!!! My cable is run through a grommet that has another maybe 1" diameter bundle of wires running through it. I think I was going for another grommet but couldn't make it happen. Its right in the corner on the firewall behind the battery. I was outside putting some lights on my grille gaurd and thought about this thread, looked and sure enough I gave you bad information. While I was in my fuse panel I realized theres another piece you might want to yank out. Its the corner piece that connects the fuse panel lid and the door sill. Jerk it out and it opens things up under the dash a bit more.

 

Sorry bro...mine was easy. I just slipped the cable through, pulled back the carpet and installation, feed it behind the black blower motor and was done with it.

There must be something else blocking it. BTW, I don't have skinny arms. lol

Maybe I should take some photos when I get home tomorrow.

 

Maybe it's the blower motor that's giving me troubles. I can't get my hand behind it from inside the cab and can't get anything past it behind the insulation from the engine compartment.
I think have an idea but I'll have to wait until 15:00 when I get home.
Pictures would be great! TIA!

 

ok i did mine a little different. i ran mine down between the firewall and battery. down behind the passenger side fender skirt where the frame piece runs. then down at the bottom i ran it into the cab. on the inside of the cab behind where are steps mount there is a pocket there with about five rubber grommets in it.i took them all out and fished the cables thru there to the back. then out at the back and right into another one in the bottom of the cab an right to the back where the amp is mounted. there is the part under the hood( 1 1/2 feet) then abount 8" right behind the skirt and then about 6" in the back. it is u.p where nothing can really get to it. for a 4 gauge cable it is perfect.