I don't know if you are talking about a get away bag or something else, nor are you clear on what scenario.

I keep these four items in my truck at all times.

1. A well equipped tool bag
2. A recovery kit in a large duffle bag and axe
3. A get away bag with all the necessities for suvival, including a small amount of ammo intended to take small game
4. LIV ceramic plates / vest with 556/9mm mags / HK P30

Now if you're talking end of the world, Russian or Chi-Com invasion scenario, that is a different matter. My plan is to exfil to a house in a more remote, less densly populated area. You need to consider for how long and how much for this one and I'll offer that you're average 50 Cal ammo can isn't going to hold enough for you to be able to defend for any reasonble length of time or take any necessary offensive action.

I will have all of the above plus several rifles and pistols plus several 120mm mortar ammo can full of the ammo I may need. I have pre-staged some of what I need in the remote location. But will need time to travel as well as time to toss the extra stuff into my truck as I don't roll that hot every day.