SM2 - the gears put you there, otherwise you could run BSP. Your car isnt really prepped for either class, but class isnt that important when you are just starting out. SM2 is your legal class, but just concentrate on getting better for your first 8-10 events. You can worry about competitiveness after that. Current rulebook can be found here:
http://www.scca.com/_FileLibrary/Fil...solo_rules.pdf Remember, if it doesnt say you can do something, then you cant.
You sure you dont mean 4.56 gears btw? The OE gear ratio is 4.10, I'd be surprised if you made the gearing taller