The above-referenced site has journals, some of which have gear lists.
THink carefully through all the weather conditions, camping situations, and bike mechanical issues you might encounter, and bring just barely enough stuff to get you through them. DOn't skimp on warm clothes & rain gear. Usually I bring 2 sets of bike clothes, 1-2 sets of off bike clothes, and enough warm stuff so that if I get wet biking I have warm & dry clothes to wear in camp. Days are short now, so you may need some entertainment for camp - I like books.
For food & water, carry enough of each to get you to the next place you can buy them, plus a teeny bit extra. SO, that usually means for me, some kind of peanut butter & jelly & bread product (bagel, bread, tortilla), or some granola bars or fruit, and 3 bike waterbottles on the bike. Look ahead on the map though - if you are at a store and the next store is 80 miles away, you probably need to add some extra food & water. Don't plan on carrying more than 2 days food & 1 days water though, as you'll just be lugging around extra weight.
Get maps before hand - AAA or state recreation maps are good for most of your trip, but you might want more detail for the SLC area, if you are going through there. At this time of year, you need to be aware of weather conditions and high passes on your route a few days in advance, so that if there's a storm coming, you don't get stuck up on some mountain pass in the snow. It's not really ok to descend big passes in the snow - climbing seems fine, and then you start down the other side and are hypothermic in 5 minutes. Do take this seriously -- I bet you know this, given you are in Big Sky, but it doesn't hurt to say it.
It's a good idea to have plan on having funds to get a hotel room when needed, especially this time of year. Don't hesitate to do that if you want/need to.
Good luck, have fun!