I have not been on these extended routes, but have canoed several parts of the Big Fork River. While not wilderness, the Big Fork is a nice river to paddle. There are a few rapids that can be run (class I-II) and maintained campsites along the river. The DNR has a map of the put-ins, campsites, rapids, portages, etc. I like the stretch from the town of Big Fork to Little American Falls. The river should be run in the first half of the season. The water level can get pretty low come August.