The climbs aren’t too bad tbh, unless it’s bloody warm. I’d imagine only the very, very top guys would spin out on say 32 X 11/42, you’ll be fine. Tyre wise, I wouldn’t over think it, whatever you have that is robust and fast rolling for the rear, and something decent volume for the front.
If it’s wet, there’s not many tyres that’ll help on the wet grassy bits anyway.
I’ll be on either minion DHF or magic Mary front, and trail boss tough/fast rear.
It’s my favourite event every year, makes the 3 odd hour drive from central Scotland well worth it….