Just t a few things to think about taking in your trunk for a variety of 
reasons....
///////
Fuel Pump
Voltage Regulator
 Water Pump
 Generator Brushes
 Distributor Cap
 Rotor
 Points
 Belts
 Hoses
 tire patch kit
 NEW oil pressure hose (very important)
 Gallon of water
 2 quarts of oil
 a gas can ( with gas in it)
 a small emergency battery or emergency pack with air compressor
a means of communication ( walkie, cb or cell phone) 
 SDC Road assistance guide. 
-------
Tube of silicone gasket maker. Lots of uses.

A roll of #14 automotive wire, black tape, and a handful of butt
splices and spade or bullet connectors. Requires little room, and
enables you to bypass a bad conductor in harness if a short should
occur.

tranny fluid, rear end oil, and brake fluid.

Roll of mechanic's wire.

Enough tools of reasonable quality to install any of the above.

Roll of paper towels, and a container of waterless hand cleaner. Set
of coveralls wouldn't hurt.

A jack you can TRUST, and a 4-way wheel wrench, or 1/2" drive flex
handle and socket to fit your lug nuts.

I carry a tubeless tire plug kit and a 12 volt compressor in my
'burban. Often easier to plug a puncture and air up than to change
wheel. 
-----------
AAA card
credit cards