If your general rules are:

1. no refrigeration

2. highly compact

3. Long shelf life

You are basically looking at using the same foods that we take backpacking. And if you'll do a search on these boards, you will find a ton of long discussions of this topic.

The one area where you may vary from our practices is that you might find it acceptable to use canned foods---which weigh a lot more than dried. But if you really are trying to fit a month or more of food into your trunk, I idon't think you'll want too much of the food in cans.

Then again, if I were car camping for a month, I would plan to eat in restaurant pretty regularly.