Gearing for touring cars really depends on the track.Small track you should gear it using smaller pinons or larger spur.And vice versa for large tracks.
So what you should do is to go down to your local track and test.See whether your motor reaches peak rpm way before the end of the long straight.If is peaking before the long straight ends then you need to use a bigger pinon until the optimum gearing is found.Remember only increase your gear size by 1 at a time.
Another thing is if your motor has not enough torque in the infield then decrease the pinon size.This is the case for the motor not reaching peak rpm at the end of the long straight.
Smaller pinon/ larger spur= faster accerleration but lower top speed.
Bigger pinon/ Smaller spur= Slower accerleration but higher top speed.
Hope this helps.
Nothings beats going down to the track for the actual track test.