Hatari: I have done a lot of day hiking and fishing in the Absaroka - Beartooth Wilderness in the past.
Take aspirin along to help with altitude sickness as I see you are from "low country".
I took my oldest son and both my brothers there once and at the time we were all from the Seattle area (sea level!) and one place we camped was near Beartooth Pass (elevation 10,947'!).
All of us had difficulty "adjusting" to the altitude.
They have had a LOT of snow up thataway this year - I hope the trails are clear for your riding pleasure by then.
Enjoy your getaway and I wish I could be more help with a horse packer - I have just never used one up there.
Hold into the wind
VarmintGuy
