THe gear reduction in a 03 with .04 gears is 2.68 to 1 and the stock .04 spur is a 63 tooth. Not sure of the .06 gears.
I'm not sure I would run a 6 turn in a 03. They are awesome cars but not sure if the tranny could handle that type of rip from a 6 turn. I ran 10 turns in my 03 at when I ran my DJ at a TCS race. I guess if you just don't punch it from a dead stoop you might be fine. I guess all you can do it try it. Gears are cheap to replace if you do have a problem.
Let us know how it is.