Oh wow! I was in Morocco last month and did that journey via coach on my way to the desert. I must say it was the scariest experience of my life! (windy mountains, no crash barrier and a driver on the phone for most of it!).
Me and my friend were the only tourists on this particular coach and the locals were throwing up left right and center! I think the journey took between 5-6 hours (an hour of which were scheduled stops) and I was very relieved to arrive at Ouarzazate. Funny that after the complete lack of alcohol in Morocco we arrived at such a desolate place with the widest selection! (they even stocked desperados in one shop!)
Apologies for the ramblings, hope the ride goes well!
morehawes.
(sorry I couldn't assist with the distance, but couldn't help write something!)