If you start at Harrah's, you go up South Grade, down East Grade, up and along Mesa Grande to Santa Ysabel. 78 isn't part of the route, so no worries there.
This route, if I remember correctly, is about 81 miles and 11k' of climbing.
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"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return." - Leonardo daVinci