On our epic 1976 "Kerouac Trip", Gumby and Robinson and I spent part of our time on one of the last remaining open sections of the legendary Route 66, namely a stretch in western Arizona that was still open because it was well to the north of its eventual Interstate 40 replacement, which opened in September of 1978.
Here's a wild story of a family of 4 (including two young "kiddies"), driving the Mother Road in reverse, starting from San Francisco, then driving down to the start of 66 in southern California before heading east to Chi-town. They have a budget of $250 a day.
The trip starts here:
http://www.sfgate.com/cgi-bin/blogs/sfmoms/detail?blogid=46&entry_id=27692