Glass windows will simply not withstand an attack. Stock pile chain link fence and store them in your garage. When the time comes, you can cut the fence to fit over every window. You will want to completely remove all side and rear glass windows first, to avoid potential broken glass. The front window can stay, because it will be harder for zombies to access, and will shield you from residual zombie splatter.
Suspension lift kits can give you a few extra inches of vertical height, which is a few extra inches of zombie that your car can mow over without damaging your underbelly. Furthermore, you can ride on larger wheels which are better for variable terrain, and if you get a huge lift kit, you can raise yourself above the reach of zombies!
Install a front hitch so you can mount a snow plow to the front of your ride. A snow plow is ideal for pushing through a herd of zombies. If you can not get a snow plow to attach to your vehicle, you should look into a front bumper guard and back bumper guard.
You may need to do some off-roading, or driving over various kinds of debris, so you will want a rugged tire with great traction. You will also need some way to repair the tires should you get a flat, so make sure you have a repair kit and air pump in the back. Hopefully, we will see airless tires hit the market in the near future to avoid this problem altogether.
Successful scavenging missions will be necessary for long-term survival, and you will want the ability to haul everything and anything you come across. Roof mounted cargo cages are ideal and can be installed on top of a roof rack.
Some basic essential supplies you should have in your trunk includes extra gas, water, a car battery, first aid kit, and a roadside emergency kit.
Reinforce the sides of your car with sheet metal, install extra lights on top, get yourself a rear hitch to haul a trailer, and/or fasten a rainwater collector to the truck bed (make sure you can boil, filter, or chemically treat the water before drinking). The possibilities are endless, and there’s no such thing as being too prepared. Remember: brains beat the brainless