I am in Seattle area and want to drive across the U.S. to Virginia
using the route with the easiest to manage elevations and
statistically least break downs.  I am driving an older Toyota truck
camper.  I will be driving in April of 2006.

Not even vaguely an answer, but you might want to try getting Google
Earth if you haven't already.

If you turn "terrain" on (you can also magnify hills in the options)
then have Google Earth calculate a route, you can have a look for
yourself what the hill situation would be like.

Have a look - it has hundreds of uses:

http://earth.google.com/download-earth.html

Good luck with the trip!

Yes, I was thinking that Google Earth might be a fun way for someone
to plan the route, especially because below a certain eye level it
also shows elevations.
But maybe road grades are more important for the question.

If you are a member of the AAA, maybe they can advise you.