I have never had my car up there yet so I am not sure. When I ran there last year with my Losi I ran Sorex 36s. Gearing wise I was in the 7.75-7.50 range. I think that a 6.20 to 6.50 might work for stock. I have never ran stock on that track. I was worried about falling asleep on the backstretch.
I would get a gear plate and run the oneway if possible. The diff will make the car push pretty bad and on that track there is only one corner to worry about with the oneway. I might try some antidive if the car gets loose at the end of the backstretch. Its an easy adjustment to make.