Needing a plan for big endurance training - Stagecoach 400

I am a fan of the podcast for quite some time. I have been a recreational MTB, gravel and riding my gravel bike on the road and I have a dedicated indoor smart trainer (Stages SB20- Zwifter). I have a friend who wants me to race the Stagecoach 400 in San Diego in March. What plan will be best for me? I need to be able to grind out long hours. Also, I am very prone to legs cramps.
What program would be best? I am realizing I need professional help.
Thanks much!



You need to build a huge aerobic base to begin with. So I would recommend our 18 week sweet spot to start off with. Then I would transition into our gravel plan. This plan includes simulation rides that you would build up in duration and distance. During these simulation rides you want to ride a course and pace that is very similar to what you will be doing for your event.