Eric,
Let me clarify a little bit(and please be aware we are currently going thru a large set of rule changes in our organization at this very moment).
Yes, your cotter pin(axle & axle nut) retainers are fully accceptable.
Yes, you need a tethered shut off switch that will shut the ignition system
off(as well as shut your fuel pump off if it has one).
Yes, you can change your transmission gearing(but I'm pretty certain that isn't your question and you are more interested in changing your drive sprockets). So with that said let me be more clear on our stance on this at the moment.
The rule states you can not change any visible items and does not exclude visible sprockets or pulleys from this statement, BUT it has always been the practice of both SCTA and ECTA(which is now more closely following the SCTA rules) that the external drive ratio of the bike can be changed(IE: visible sprockets and chain or belt if needed).
So in answer to this question(again, at this time):
Yes you can change your chain sprockets(or belt pulley as the case may be), as long as it is
of the same style(IE: it is not a drilled & lightened sprocket, etc.), and it still uses the same pitch of chain or belt that the o.e.m. did.
Yes, you need a metal chain or belt guard in production class,(we have allowed OEM in the past, but we currently "by the present rule" do not).
Eric, we look forward to seeing you at the track and you can feel confident
that you will be able to run as long as you have the safety end of things
squared away.
Todd
EDIT: There will of course be some 30 day(one meet) grace periods granted to members in regards to the rules that have changed from 2007 to 2008(as well as concerning the rulings that might change throughout the season). Our goal is for you to run and have a good time, our responsibility is to try and help you do it in a safe manner while being fair to our other members(both past and present).