Welcome, Ian!
CFRSCCA is a good group of guys. No shame in running with them if it's convenient for you. (DLB is just their event registration site, btw. We use one called MyAutoEvents.) They've been at it a lot longer than we have!
I'm not going to try to specifically answer your SCCA classing or safety questions, but I'll throw some basics and some common sense at you:
First, without getting into a deep discussion of all of the whys, your car is probably in one of the SCCA Modified classes. Probably D Mod, if I recall correctly. But, if all else fails, as long as it's safe, it can probably run in A Mod. Let them figure it out.
For FAST, you're in R1, our race tire class for "race cars". It falls there because it's on tires that don't meet our street tire requirements, and it's modified beyond our allowances for the standard Mod classes. If it weren't for all the cutting and welding, you could probably have run it in R2. And, if you opt to put street tires on it, you could run it in M0 (Open Modified Street Tire).
Being essentially a "constructed" car, for SCCA, you'll have to read through their Modified rules to see what their requirements and restrictions are. I suspect they will be very thorough... and they may very well redirect you to SCCA Club Racing prep rules for certain safety things. FAST has a few safety rules that would apply. But, we get so few cars like yours that we haven't bothered writing a bunch of specific rules. We'll just do a thorough inspection of your car and let you know if we see anything that warrants attention.
A couple requirements: (as per our insurance company)
- Any open-roofed car on non-DOT tires must have a roll bar.
- Any open-roofed car using seatbelts with more than one shoulder strap must have a roll bar.
- Any purpose-built race car must have a roll bar.
- No Nitrous Oxide bottles are allowed.
I'm sure your car fits in one or more of those categories, so a rollbar would be required. We don't have specific rules for a rollbar, but would recommend that you build it to SCCA specs. (while also looking at NASA specs, and maybe even NHRA specs... a minor change in design here or there can ensure that you are in compliance with ANY rules, as well as keeping you safe)
A parking brake isn't required, but it's a really good idea. You don't want your car rolling around the grid bumping into other cars! If you don't have one, keeping a couple blocks on-hand and being extra careful should suffice.
Things we'll be looking for beyond our standard safety checklist: (just off the top of my head)
- Complete firewall. If there's an engine fire, we don't want flames reaching YOU.
- Appearance and routing of fuel lines, brake lines, coolant lines, etc. Fuel lines and brake lines especially must be securely mounted and routed so that they are not near very hot parts, such as the exhaust. Any such lines in the cockpit must be fully metal-enclosed.
- Things that could rub that shouldn't. Everything from the lines mentioned above to tires and anything else that could become a wear problem if allowed to rub against whatever it's rubbing against.
- Driver safety. Seat mounting, seatbelt condition and mounting, roll bar height, protection from debris on course, etc.
- We don't require it, but for a car like yours, we highly recommend either a fire suit, or at least long sleeves and long pants of heavy cotton.
- General appearance. Does this car look like it's going to get around our course without killing the driver or injuring our course workers?
Yes, you can (and should) mount your extinguisher in the car. Needs to be a sturdy metal bracket very securely mounted to keep it from becoming a projectile.
All that being said... I'd really recommend that you come at least do an event or two in a more mundane car just to learn the basics of autocross. Most people find that overwhelming enough without the added excitement of an unpredictable custom-built race car. Also, our Novice School is November 1st. Highly recommended... and, again, would recommend doing it in a car that doesn't require you to think about the car so much so that you can "just drive". Even a rental car, if you don't have anything else in the stable.
Learn the basics of autocrossing first, then you'll be more ready to handle FrankenMidget!
