All those highways are very good.
Hwy 89 to 89A to 67 and the North Rim of Grand Canyon is an easy drive. Keep in mind that leaving the North Rim you'll have two choices:
- Continue on 89A - you'll have a steep decline as you leave Jacob Lake but with your motorhome you can easily do it. Many RVers and semis do. Then it's a easy drive to 89 and south to Flagstaff and I-40 (not I-80 as you stated).
- OR..after leaving the North Rim, head north to Kanab, UT and pick up Hwy 89 to Page, Arizona and then south on 89 to Flagstaff. No issues except a decline from Jacob Lake to Kanab but not bad.
Full-timed for 16 Years
. . . Back in S&B Again
Traveled in a 2004 Newmar Dutch Star 40' Diesel