Welcome to the site. We follow SCCA classing and rules. Those documents can be found here: http://www.scca.com/contentpage.aspx?content=61
From your description, I think you would be in the Street Modified class just because of the motor work. As far as safety equipment, you really just need to make sure that your battery is tied down, your car is roadworthy and you have a helmet. If you don't have a helmet the club has loaners that you can borrow.
My first car was a 1990 LX 5.0. I put an E cam, Cobra intake and a few other bolt-ons on it in addition to a bunch of suspension work. I started out drag racing as well. I only ever ran 14.0s at just under 100mph, the stiff suspension killed my 60 foot times. I got into autocrossing in college and have been hooked ever since then. My dad has a 95 Cobra with a 331 in it, AFR heads, custom cam and a Kenne Bell that he autocrosses. They are fun cars.
Our next event is actually going to be a novice school on April 25th, followed by an autocross on the 26th. You can register for the school here on MyAutoEvents
. You can learn a bunch about driving your car and how it handles in an inexpensive, safe and fun setting. Hopefully I'll see you out there.