[dynomatt]

I'll try and answer some of the questions more clearly. I should add, I have no idea what your "street legal" requirements are so make the assumption that everything I suggest renders it illegal, unless you can work out otherwise.

• Dry ice - yep, dead easy, photos are in the rally car thread
• Seats - I used Sparco Evo II seats. They mount using side mounts, and have a strip welded to the floor for them to bolt to. Plenty strong enough.
• Harnesses use the original seat belt mounting points on the floor (either side of the seat) and loop around the roll cage at the back
• Airbags - everything gone (wiring, sensors, bags ECU etc). More dangerous with them if you have seats and harnesses. Helpfully, any wiring to do with the airbags is wrapped in bright yellow tape, so it was very easy to find and remove
• Climate AC - I only use mine for demisting the screen. So it's locked on heat setting (when you pull the heaterbox apart you'll see what I mean). All the solenoids, wiring, ECU etc are gone. One switch remains to turn the blower on and off.
• ABS - all gone...wiring, sensors, modules ECU etc. Not needed.
• roll cages are custom sized. None of the shelf are avaialble, and I would warn against trying to fabricate one based on measurements.
• Weight reduction - ongoing. Bumpers have 3 parts, outside plastic skin, foam padding and massive steel structure. I removed the foam, reduced the steel structure (by cutting with an angle grinder) and reduced the weight a lot. I've also pulled out the second firewall (there's twofor NVH). Once the car is stripped, and you realise its intended purpose, you'll be surprised what you don't need. Glass, electric glass winders, sunroof mechanisms, pointless bracketry
• Suspension - see the rally car thread for the spring rates. Yours will be different if it's for track. Springs will be a lot stiffer, valving a lot firmer. Strut tops, I used generic solid ones and customised to fit.
• Stock brakes with high quality pads are fine. Anything more complicates it.
• Engine oil cooler - can get sandwich plates to go between the filter and the block. WRX's run a water cooled oil cooler that will also fit.