I had great success with a similar sounding race this last summer using climbing Road Race specialty. I live in Florida so the only thing I wish I did was more low cadence work on the sweet spot intervals and extending my time in the sweet spot zone.
I think the Gran Fondo plan is the century specialty which I heard is even better for long events like you’re talking about.
I’m actually going with the century plan this year for the Belgian wafer ride in Asheville. I’m going to work on some low cadence work because Im a flatlander.
I’m also interested to see what others advice is for you But I’m pretty confident with what route I am going.