I have a spare tube and pump under the rear seat along with irons, i live in mennonite county and the horses throw nails all the time.
2L bottle of water for the rad if need be, points and condensers (with nurex wrench), coil, bulbs and water pump packing and gasket with tools.
Basic tool kit to go along with it. A 6V circuit trouble light is a great thing to have as well as it lets you check for voltage throughout the car and don't forget a good flashlight and USB charger unless you have converted to 12V