What sprocket and ratio should I go for on my first mini bike?

Hi everyone,

I'm looking at building my first mini bike and I'm not sure what sprocket size to put on and what ratio I should go for. It's going to be a lightweight fat tire bike similar to the one jeep2003 built. I'll be using on muddy/ hilly terrain. This is what I'm thinking so far

Predator 212 6.5hp
Torque converter with 10t sprocket
#41 chain
22x10 tires on 8" hubs

I was looking at ratios and I heard 9:1 was good. Is this correct? If so I would need like a 90t sprocket in the rear. What do you guys think?