I THINK that 2005 is the oldest SA rating now you can run. I'm not 100% but when we had our solo board meeting a few weeks ago it was brought up and IIRC, they said that the old helmets would have to go.
http://www.scca.com/documents/2011%2...lo%20Rules.pdf
there's the link to the SCCA's solo II rules. If we can't run an SA2000 helmet, I'm sure the HPDE/TT guys can't either.
I would check into the GCR's latest specs and see what they say about rollcages. I'm not sure what NASA's rules are like, but maybe they allow different cages in their sanctioning.
Hope that helps.