Hey when you come out for SSC... let me know !!
Wow... do I know what your dealing with.
I too am building a 67 f-body... that has to meet the rule's of three different sanctioning bodies. Please allow me to offer this advise...
get all the rule books from the different sanctioning bodies you plan to deal with, and find out what works with what. It will save you tons of headache when dealing with the cats in tech. For instance... its a great idea to "taco" the a-pillar bar to the body and part of the halo to the roof line... and it works for one sanc body... but its illegal in another !! So before you do anything... read up !! Because I am sure you don't want to do things twice... just to make one of them happy.
Food for thought. I am going to use 1 3/4 x .120" for the main structure (the cockpit four point) and then you can use 1 5/8 for the support structures to keep the weight down... without sacrificing strength where it needs to be.
FWIW... I do technical inspection for SCTA/BNI... so I am in the midst of the issues in the 'science of safety' and am actively involved in the direction of making it safer and hopefully setting standards across the board. More specifically, I specialize in dealing with fire suppression systems, roll cage structures, restraints, seats (with emphasis on lateral head restraints), roof flap systems, drive-line (obviously) and at Bonneville this year... fuel systems. So yeah... I know where your going on you safety mission. Keep it up man... learning as much as you can is the right way to do it !!
In specific relation to roll cage structures and the ECTA (which actually follows the majority of the SCTA/BNI rule book)... the ringer statement is, "Vehicles in classes where the existing record exceeds 175MPH must use the larger tube minimum requirements." I can pretty much bet that you will be classified in "Classic Gas Coupe"... and depending on your power plant I think you will most likely be classified in "Gas Coupe." If you swapped in an LSx or something other than was a factory offering, it will depend on where it will place you in the "Production" or the "Modified" category.
The good thing with the seat issue... as I myself use to drive long distances, constantly, with the same idea of comfort... but the new seats, are so damn comfortable... who knows. But in all actuallity... you will only need to bolt in the "Kirkey" for the events you run... and you can always run your regular seats until the required weekend.
As you can see, I have just gotten the chassis to the point where I can get the 108 ft of 1018N tube installed... and had to get the seat in my hands to get its position down to where I can now configure the tubes around me, the driver.
I think ya gotta know just how much room you have or don't have to really figure out where critical tube placement needs to be so it doesn't end up to be a jungle gym.
Ahh yes... the illusive 2. Rules also limit you to what you can and/or cant do in terms of aero modifications. But... I do know... it will take you about 650 to 700 HP to get into the 2's in a second Gen !!
Other notes...
Suit. You are gonna need to get a minimum of a 15... boots and gloves, minimum of 5... for any work 175 MPH and up. For comfort, I would get a two piece suit. If it were me I'd get a 20 two piece, 15 boots and gloves. You are the most important part of the equation... don't skip on PPE. In this arena... if you go over the minimum, your covered in all other sanctioning bodies.
Helmet. I would get something that has top or side feed air. For the super cheap... you can get helmet forced air systems for not only the fresh air requirement of some rules... but it makes a HUGE difference in comfort. Why sweat when there are cold air systems, or you can even make you own, really really cheap. I'm installing a Cool Shirt Pro system with both air to the helmet and water to the suit... just because if you have ever spent anytime in a suit and especially waiting in any kind of line to take the course... its all worth it in terms of fatigue.
Anyway... enough of my rambling... keep me up on your project. It sound like a fun build.