6/30/97: Update from Dave Robertson from Adventure Cycling.
On the map near Park Lake, (between Helena and Basin), note the two miles on the road marked 1878-D. It is listed as a steep and rough 4-wheel drive route. This is no exaggeration. Plan on possibly pushing bikes on parts of this stretch. It is about 2 miles.
There is no longer a grocery store in Basin, as listed on the maps. The nearest one is reportedly in Boulder, 10 miles E/NE by Interstate. There is a cafe in Basin.
The "non-maintained cattle access trail" which parallels the Interstate from Basin is much more enjoyable than it looks. It is often isolated from the freeway and maintained better than the FS roads.
When approaching the Interstate near Dillon, go past the Interstate and turn left onto the frontage road. It will take you to town where you'll turn right onto Atlantic this will take you toward downtown.