[mfain]

There are three pretty good road racing bodies in AZ, NV. SCCA, NASA, and Proautosports. You can access their rule books (and their schedules) on line, and there are a few differences. For example, NASA doesn't allow any bends in the back braces to the main hoop of the roll cage. They have slightly different weight breaks for roll bar tube sizing/wall thickness. One requires a dash bar, another makes it optional. SCCA doesn't allow aerodynamic side skirts.....You get the idea. I just spent three weeks updating my car to be in compliance with the toughest rules -- had to move the diagonal brace on the main hoop to cover "75% of the vertical height", move the battery cut-off switch, and add a metal (.050 aluminum) bulkhead between my fuel cell and the passenger compartment -- mine was originally fiberglass. I would recommend that you print copies of the rule books while you are still building your car, which looks great by the way. They also list tech reps/phone numbers and provide a process to apply for waivers -- better to get the answer now than after the car is finished. Complying with either SCCA or NASA rules will also get you in the Nevada/Silver State Open Road Race (which also has rules available on line). As to your question about classes, if you want to compete for National points, there are very specific rules (weight, horsepower, modifications, tires,etc.) for each class. However, if you are out to race in High Performance Driving Events (HPDEs), club days, or track days for fun, all you have to do is satisfy the safety requirements and you're good to go. NASA (or SCCA, I can't remember which) also has a Camero-Mustang Challenge series that looks like a ball.