We did a trip without the trailer in 2012 along most of the route going to Phoenix. Some of the sights we used from MI were the Springfield Zoo, Galena KS to see Mater from Cars, OKC bombing site, Cadillac ranch in Amarillo, and others.
POI Factory has a download for your GPS that will give many of the sights along the old route.
There are several other websites that list the sights like
Roadtripusa.com . You can also find forums that are only for the route like
Historic 66.Have fun, take your time, and learn as much as possible.
Dale