I’ve been doing Blue Ridge Adventure races for over a decade now, they do a great job. I’ve done ORAMM 3-4 times over the years so I’m probably not going to do it this yeah. I’ve been focusing on their short course versions, which in that case is the Jerdon Mountain Challenge. 30 miles and less than half the elevation gain. Good luck - I would focus strongly on sustained build after working in a strong base. Then go to the marathon XC specialty. It’s a long day for most riders 6 hours plus.
Do you live in the area? I haven’t met any local TR users yet.