2009 rulebook
http://cms.scca.com/documents/Rally%20Rules/2009rxr.pdf"A RallyCross event is open to any fixed-roof production based vehicle (including
convertibles with a factory hardtop attached, targa-types with factory panel in place,
t-tops with factory panels in place) that can pass safety inspection. If the Event
Chairman after consultation with the Event Safety Steward determines at his discretion
that a vehicle cannot safely negotiate the course, it may be excluded."
Stock Rear Wheel Drive (SR)
Stock Front Wheel Drive (SF)
Stock All Wheel Drive (SA)
Prepared Rear Wheel Drive (PR)
Prepared Front Wheel Drive (PF)
Prepared All Wheel Drive (PA)
Modified Two Wheel Drive (M2)
Modified All Wheel Drive (M4)
most pump fuels can be used like diesel and E85, the Modified is basically the catch all. You would have to read the rulebook for further details, to save me the time of retyping.