Oil pan, buy the Katz pad at NAPA, buy some high temp silicone goo(one tube is plenty), buy roll of duct tape. Get under car, put silicone goo on clean oil pan, duct tape in place so it holds really tight. run cord so it doesn't hit hot or moving things. If you have enough room to put a power box under the hood you should it makes everything really clean, my Impreza had one and I loved it.(little metal box bolted into the inside of the engine compartment, with 4 outlets in it). then run that cord out of the front.
Battery blanket(it wraps around the battery), take battery out of rig, wrap around re install battery with it wrapped around. problem solved. run cord as before to power strip.
If you feel the need buy a trickle charger(I never had one and was fine but hey after 7 winters up there what do I know).