Rmolina, in 2010 I did Granite Pass heading east from Cody/Graybull to I90 on Sheridan. Wouldn't do it again. West side of the pass was steady up hill climb, very long, east side was very steep with numerable switchbacks, much shorter but more hair-raising. I was glad I was just towing a Casita not something else. You've probably made your decision now and are committed so if you're taking 14 west good luck.
In 2013 I was headed west from SD, got off I90 at Buffalo, WY, and took 16 west to Worland, then up to Graybull to Cody. That pass, Powder River Pass, isn't nearly as steep/challenging as Granite Pass. I was heading to Cody, then into the east side of Yellowstone so the route made sense to me.