There's a grommet up under the driver's side dash that leads through the firewall - it's directly above the brake-pedal arm. Under the hood, the other side is right behind the throttlebody about 10 inches down from the TB.
Mount your fuse and distro on the relay box casing behind the battery, route the wires behind the intake and under the crank-vent hose.
The dash comes apart easily; pull up on the trim near the cupholder, pop the top of the center console out at the dash, and it slides off. There's a harness for the HVAC to remove. Wires down the back (pleeeeeeenty of room) then behind the carpet (at the front of the cabin) and down either side of the doorsills.
b-pillar trim pops out enough to fish the wires through, backseat comes out like every other seat on the planet - pull up, and out.
In the hatch there's a panel that has the flat-tire tiedown buckles, beneath that is plastic; You can screw a distro onto it without damaging anything.
Watchout for the scosche dash kit, it's a piece of shit and a pain in the *** to assemble - it needs to be trimmed to fit right, they made it universal.
The radio door doesn't close over my PRS880, be aware of that.