2011 SCCA Rules:
14. STREET TOURING CATEGORY
14.1 AUTHORIZED MODIFICATIONS
All Solo Rules Stock Category allowances, plus all allowances contained
in 14.1 through 14.10.
14.2 BODYWORK
A. Pedal kits ...
B. The driver and front passenger seats ...
C. Factory rub strips, emblems, mud flaps
, bolt-on front valance lips/
spoilers, and fog lights (except those integral to a headlight or turn
signal) may be removed.
Implication is that in stock, you can't, but I didn't find it directly. ST isn't a bad class to run in, and depending on what you are using for tires, might even be a better class.
Good luck.
Mike