I posted this in the other thread, but since you started a new one, I'll answer here as well.
Go to an SCCA regional licensing school. Once you have your SCCA novice permit, you can apply for a NASA rookie permit, and race W2W immediately with both NASA and SCCA as a novice/rookie. Two races with SCCA gets you a regional competition license, 4 races with NASA gets a
competition license. My SCCA school with San Francisco region was ~$500 and I got ~ 6 hours track time, plus 2 races over 3 days.
When you put the cage in your car, make sure is complies with SCCA Improved Touring specs, and you can probably race in regional Improved Touring "E" class, even though a 911 is not a touring car. I know in the San Francisco SCCA region ITE is pretty much open, the only rules are any tub chassis production vehicle running with DOT tires, and the car must meet Showroom Stock or IT safety requirements. You can read the SCCA rules
here.
Unfortunately CalClub (SoCal SCCA) is much more restrictive for ITE class, with limited mods, and a Fuel cell required, but still doable for a street driven car. Details
here.
Tom