No, we don't have any SP stuff on the site, sorry

We stick with Stock and Street Touring, since that's what we know.
My opinion: don't tell anybody about the flywheel and clutch, and run in STX. As a beginner at the local level, it's not gonna matter.
To be 100% within the rules, I'm pretty sure you'd be in Street Modified, but here's the breakdown as I see it:
Obviously you can't run stock class

Next best -- STS -- can't run that with the fixed-back seats, the motor/tranny mounts, or the flywheel/clutch.
Next best -- STX -- motor/tranny mounts and seat are OK (although the Sparco might not be, it depends on how it's built -- that rule is particularly funny). Clutch and flywheel are *not* OK though.
Next best -- DSP -- strangely, the motor/tranny mounts aren't legal. Everything else would be cool.
Next one -- Street Mod -- everything you've got is legal, and you can even bolt on a turbo kit. Unfortunately, you'll probably get soundly trounced there.
Like I said at first, if you can get by running STX locally, that'd be a good spot. You could probably even squeak by in STS in some situations, but the race seat is a pretty obvious no-no for STS that people can easily see, and somebody might call you on it.
I want to empasize that I am *not* encouraging you to "cheat" -- just that as somebody new to autox you shouldn't be overly concerned with where you'll fit. Go to a local event and have fun. If you get hooked and start to get good, pick a class and either add or remove stuff to make the car fit the rules for that class. Street Touring (STS and STX) were specifically designed as classes to attract folks like you that have modified their cars a bit and want to try autocross, your car is quite close to the STX rules, so that's where I'd personally place you if I was the guy helping with novice classing at an event.
Of course, all this is just my $0.02.
Good luck, and most importantly, have fun.
Sean
www.subrew.com