Gravel race training approach

Hello, I need some help deciding how to aproach my training for a gravel race in my country Guatemala in may 15 2021. I am currently training for a MTB stage race in march in the specialty phase. I am just 6 weeks apart for this 4 day xcm stage race. I plan to start training after one week of recovery after the stage race so I will have 2 months until the gravel race. The gravel race will be 100 miles with at 5000-6000 meters of climbing, The amount of climbing is what I am afraid the most. Have never climbed so much in one day. I plan to do the gravel race in a hardtail mtb. I have never been in a gravel race, and this one is the first edition of a gravel race in Guatemala. Give me your thoughts on wich training plan should I focus on.

Here are two default resources that are worth a look: