was looking at this site,
http://www.expeditionfoods.com/aboutfoods.html
and at around 300-600 kcal per 100g, your 55lb works out to be around 25kg, so thats 250 portions of food (100g), say with an average of 400 kcal/100g, you'll get around 100,000 kcal of food, not inclusive of packaging weight.
If you look at the non freeze-dried foods, you'll see that the average calories per 100g maxes out at around 200 kcal/100g. You could get pemmican, though, which was the preferred food of the earliest artic explorers like Scott and Edmunsen. Its basically a VERY fatty and high energy blend of foods.
No way you could get by without dehydrated foods on your weight budget. Even beef jerky has only 270 kcal/100g.
oh, I have no affliation with any of these sites. I haven't even heard of this topic prior to this thread (other than the info about artic explorers..heh.)
You'll definitely need multi-vitamins and whatnot to supplement your nutritional needs.