Somewhere on this forum there is a relatively recent thread about the pass. I rode it last year in the opposite direction. Heading from Hamilton, once you cross the pass the descent was mostly soft dirt. Then there is a random paved stretch before it turns to dirt again. Once you reach Gem Mountain, the pavement picks up again. There was a washout on the Hamilton side of pass so a portion of the rode was oficially closed to traffic, but I was able to make it through. It is a fun ride. I was riding an LHT with 37c Conti Top Touring tires.
When do you plan on trying it? I rode it in late June. There had been a lot of rain so the dirt portion was a bit spongy. Just as I started the descent towards Hamilton I got caught in a torrent of cold rain. I would consider having a good rain jacket and war, gloves if you could hit some cold weather.
Note that the only thing in the way of food and drink is at Gem Mountain. They have bottled water (no potable tap water), sodas and snacks/nuke-able sandwiches. I stopped there, bought a bucket of dirt and walked away with 16.25 karats of small sapphires. Continuing on to Butte, there will be a still climb once you turn on to MT 1 from MT 38. At the top, next to Georgetown Lake, there is a marina with a small store. Never been in, but the sign suggests they sell beer and thus probably soda and snacks. For a while you cruise pretty flatly along the lake. A little after Silver Lake it's all down hill through Anaconda to the junction of MT 1 and I-90, where there is a highway rest area with water and bathrooms.
This photo to the last three of the album set were taken on MT 38, going in the opposite direction that you will be:https://www.flickr.com/photos/davez2007/14370757537/in/album-72157645062932708/
Note that you can make it from Anaconda to Butte without riding I-90 if you don't mind some more gravel. There is a trail which takes you up the hill into the old section of town. The camping in Butte is not so nice. I recommend treating yourself to a room at the Hotel Finlen. The motor lodge portion of the establishment is basic but well kept, and it's right in the old section of town. Throwback to an earlier era. The first year I stayed there my bathroom had a bright lemon yellow toilet, sink and bathtub/shower. Get a room on the first floor and you can roll your bike right in. The place also has a retro bar/lounge that is neat. Let me know if you want the exact route and I will map it for you.