There are no unpaved sections on the stretch I outlined. I've ridden it.
You can ride all the way from the Grand Canyon thru Window Rock to Abiquiu.
All pavement, low traffic. Services comparable to the Western Express.
The unpaved part is a zag to Chaco Canyon NHP. Well worth it.
This park includes some of the oldest and most extensive ancient Puebloan ruins.
Speaking of history. And I do teach college history.
The fact is - Route 66 in Arizona and New Mexico has largely disappeared under I-40 since the 1970s.
Yes, there is the fabulous section thru Peach Springs. But between Flagstaff and Albuquerque it is questionable.
In many places the old road from the 1930s is a streak in the desert.
Where there are maintained sections, they often dead-end at a fence on the interstate.
And when there is a usable service road, it can be right next to 20,000 vehicles on I-40.
Nearly everyone who has tried to ride Route 66 has complained about this section.
If you reroute a little bit - i.e. onto Townsend Winona Rd - you are already "off route".
And if you are riding on I-40, you are certainly not riding on historic Route 66.
Although I am not absolutely against riding on an interstate - it defeats the purpose of touring IMO.
I won't detour 100 miles to avoid 5 miles of interstate riding where it's the only option - -
But to plan a route that includes considerable mileage of interstate and service road riding is less than ideal.