Brad,
I haven't been on the Marathon, too many other things to do during the Jam. I have talked to quite a few of the riders though and looked at what they take.
It seems that you get just about everything.
Since its three days some guys will just load a cooler of your basic food. Others bring MRE's.
Personally I like MRE's. The food is really quite good. If you haven't tried it lately it is amazingly better than you might imagine. Price is not bad and you can't beat the convenience.
I like this website for MRE's, great selection and some decent combined packages. Multimedia file viewing and clickable links are available for registered members only!! You need to

or

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This site seems to have a good price on a 12 meal pack Multimedia file viewing and clickable links are available for registered members only!! You need to

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so does this one Multimedia file viewing and clickable links are available for registered members only!! You need to

or

!!
Lots of places. Make sure they are MilSpec MRE's. There are a bunch of companies selling "MRE's" that are not MilSpec and while they might be okay I wouldn't trust a non-milspec MRE to last a year. BTW, MilSpec is a specification, not a brand name even thought there is a "MISPEC" brand MRE. Confusing huh. Most place are sold out of MRE's, they all wne to IRAQ.
I think I'd be too busy riding and talking to want to spend much time messing with cooking anything on that ride so the MRE makes a lot of sense.