Offhand I can’t suggest specific spots for a 40’ RV. But in AZ there’s a lot of national forest and public land that you can boondock on. You’d just have to watch for an open area near the pavement that you are able to maneuver onto. And they are there. There are other posters with big rigs that may be able to give you better info on specific spots, too.
Another thought, by late November anyway you can expect winter storms in the higher elevations, e.g., Flagstaff and I-40. Not a problem if you’re taking that route in May or June, otherwise keep your eye on the weather so you don’t get stuck somewhere.