I raced with SOVREN for 3 years back in the 90's. It was much more relaxed back then - probably more like it was back in the day. There weren't as many ginormous mega dollar motor homes and semis with traveling mechanics in the paddock.
Back then, 911's were top dogs...as will be the case when you're running a 2Klb car with a (rumored) high strung 3.2 cleverly disguised as a '69 911S motor. It was not uncommon for 911's to finish 1,2,3 in the over 2 liter class.
Here's a link to the rules.
http://www.sovren.org/competition/competition.htm