Don't know how long it's been since you've been on Priest Grade, but it's only 5 miles long and it's been widen and improved in the last 10 years. Tour buses and semi trucks go up and down it all the time. I don't even consider it an obstacle on Highway 120.
My last time over 120 from the valley was last year. It's a verry long & steep 5 miles. I got stuck behind a family in a rental car doing 5 to 10 miles per hour. Lot's of fun trying to keep up momentum. No way I would do that in a 40 footer with a toad, no matter how many tour buses and semis go over it.