This is from NHRA's site (
http://www.nhra.com/content/news/33870.htm)
Stock
Jacket and pants meeting SFI Spec 3.2A1 mandatory in AA/S through M/S, AA/SA through M/SA, and in any vehicle running 11.49 or quicker.
Super Stock
Neck Collar: Neck collar meeting SFI Spec 3.3 mandatory in all cars running 9.99 (*6.39) or quicker or cars exceeding 135 mph. A head and neck restraint device/system may be used in lieu of a neck collar.
Jacket and pants meeting SFI Spec 3.2A/5 mandatory in SS/A through SS/I and SS/AH through SS/IA, AA/SA or any vehicle running 9.99 or quicker. Jacket and pants meeting SFI Spec3.2A/1 mandatory in SS/J through SS/P and SS/JA through SS/PA or any vehicle running 10.00 to 11.49.