What would adding the Getrag 6-spd to an otherwise stock MC do to your classing? Come to think of it, I also have a new intake, so I guess it's not strictly stock.

But ...

 

I think it would either bump you into EP or maybe SM depending on who is reading the rules.

If you are just getting started in the sport, let the organizers know you are new, and they will likely put you in a novice class for the time being. That will give your club time to know where exactly you should move to.

Thing is, in the regular cooper, it really doesn't give you a huge advantage in an AX course, the stock 5 has a 8.33:1 2nd Gear ratio vs. the 7.79:1 in the 6 speed. Unless you have someone who is laying out wide open courses where you are able to get a Mini (or S) up to 55-60mph for extended periods of time, you likely wouldn't notice too much of a difference.