I would do it the reverse of what I posted that Dave said about 3.29's.
Start with the stock 3.29 Comp Table, I'd expect it says 3.69 gears. Plug in 3.29 and the tire size then commit with the auto scale on. Poof...
I just pulled my stock Comp Table and it still says 3.29 for calculated gear....so would I have to plugin 2.93 after the gear change? This may be more of a pain then its worth