Dirk,
I would stop by the meteor crater (
http://www.meteorcrater.com/index.php) on the east side of Flagstaff. The Petrified Forest (
http://www.nps.gov/pefo/) And the Grand Canyon (
http://www.nps.gov/grca/) is always a good trip but it is about an hour off the main drag. Montezuma castle (
http://www.nps.gov/moca/) near Sedona is cool. One of the best little towns that once was a cooper mining town, stuffed into the side of a hill is Jerome which is on the road between Sedona and Prescott. It is up around 7000ft so it will at least be cooler than Sedona. If you go there spend the $$ to go into the mine camp on the NW side of town and grab a burger at the local bar (called the Spirit Room) before you go.
A guy that owns a Cobra (FFR, I think) runs a parts store in Prescott on the corner of W Gurley St and Grove Ave. I’m sure if you broken in town and stopped by he would be able to help, I think it is names Allison Automotive. While you are there a walk down Whiskey Row and stopping to get a bite at the Gurly St Grill (230 W Gurley St) is suggested.
If you are into driving through turns you NEED to leave Prescott to the SW on White Spar Road. It contains 40 miles of pure turns. You will know when you are at the bottom when you see a long 5 mile down hill straight that ends at the local bar/ sandwich shop. In the middle of the turns are a few small town Peoples, Yarnell, … Take a right onto 93N and that will lead you back onto 40. Or if you have the time continue down to Parker then N on 95 through Lake Havasu and then onto 40.
I would suggest taking a 5-gal gas can sometimes there can be long distances between gas stations. And add some Red-Line Water Wetter to your radiator it will help with the heat.
I remember taking a similar trip with my dad when I was a teenager, we were in a 1970 VW pop-top camper, it was a blast. I ended up living in Prescott during 90’s for a few years. If you like outdoor stuff you can beat it.
Have fun,
Rob