Showing up to your first autocross and cheating isn't usually the best way to make friends.
Besides, if you've never autocrossed before, you're not going to be remotely competative no matter what class you're in. Check to see if your local region has a Novice or Street Tire class, and just run legally. Your goal for your first 10 events or so should just be to go faster in each consecutive run. Don't worry about anyone's times but your own. Learn the line, learn to be smooth.
As far as tech... it's not their responsibility to class your car, it's
your responsibility. They're just there to make sure your car is safe.
And tranny swaps = Street Mod. Unfortunately, unless you turbo/supercharge and prep an SVX to the limits of SM rules, it will probably never be nationally competative in SM. However, lots of regions don't have a big SM following, so there is the chance that you may be successful in SM at a local level as long as no one with a fully prep'd SM car shows up regularly.
Edit: benebus pretty much beat me to the punch on all my points!
