The best way to go is a nice crew cab pick up. Something with a low profile that you can drive through the doors of a Costco and take all of Britt's stuff and still seat 4-5 people (I'd stick with at least 4 people when doing anything). Weld some chainlink fence on the windsheild and rear window and rebar over the door windows and you're good to go. If you're worried about other survivors shooting at you get some 1 inch steel plates for the doors and around the engine block that you can easily replace and viola' perfect zombie vehicle.
CrowBar I'm resisting posting a picture of a Nissan
Frontier LOL!