I've found that the Benchmark series of maps (in large booklet format, by state) have good detail down to backroads, including fairly accurate indications of which roads are paved and which are dirt (very useful when trying to determine if a certain backroad is actually going to be a good option or more trouble than its worth). There are some forestry roads around where I live (northern California) which the DeLorme maps don't indicate as being dirt, but the Benchmark does. Although these maps are about $20 per state, you could just treat that as a cost of the tour and tear/cut out just those pages you want/need. Here's the California one, for reference - they do many other western states:

http://www.amazon.com/Benchmark-Cali...dp/0929591496/

Neil