One thing I found out was a good and lightweight substitute was Coast Guard approved survival food bars. I got some in cinnamon and some in lemon. They last forever compared to MREs and have just as much food value.
You can carry a week's worth of these bars in your glovebox where that many MREs would take up much more space. These are typical:
https://www.firesupplydepot.com/mayday-food-bar-3600-cal-fb36m.html?cmp=bingshopping&kw=mayday-food-bar-3600-cal-fb36m
I also found another brand in the Wal Mart camping supplies aisle.
Coast Guard food bars? They must be good, judging from the weight of your average Coast Guard petty officer.