Dr Gregory Davis and his wife Lynn have entered GAMRR in 2018 & 2019, both times in different Hudsons.
Following is a link to his blog which covers all three days of the 2019 event.
Please check it out; some great reading and will give you a real feel for what this event is about.
https://www.gregorydavisdds.com/blog/2019/11/02/2019-great-american-mountain-rally-202395