This is from the 2011 rule book from roll cage section. If anybody wants a copy of 2011 rule book PM me your email and I will send it to you.
ROLL CAGE
Roll cage mandatory in cars running 10.99 (*6.99) or quicker or any
car exceeding 135 mph. In full-bodied cars, with unaltered firewall,
floor, and body (from firewall rearward, wheeltubs permitted),
running between 10.00 (*6.40) and 10.99 (*6.99), roll bar permitted
in place of roll cage. In convertibles running 10.99 or quicker or
exceeding 135 mph, roll cage mandatory. Cars running between
7.50 (*4.50) and 9.99 (*6.39) must have chassis recertified every
three years by NHRA and have a serialized sticker affixed to cage
before participation. Plating of chassis prohibited for all cars
manufactured after Jan. 1, 2003. Rear-engine dragsters must
conform to SFI Spec 2.7B; vehicles running 8.49 to 7.50 and/or
exceeding 180 mph must meet appropriate SFI Spec for body used.
Effective Jan. 1, 2007, all new Street Roadsters must conform to
SFI Spec 10.4. Existing Street Roadsters must meet SFI Spec 10.4
at their next scheduled recertification effective Jan. 1, 2008. No
existing cars will be recertified early to delay compliance. All others
must conform to specs for body style used, as listed in General
Regulations 4:11, 10:6.