560 cubic inches max for BBC, and anything goes on interior engine mods, as long as it breathes out through the cast iron exhaust manifolds and a 2 1/2 inch exhaust system. Otherwise, the class is what it says, Stock Appearing.
Here are the rules.
fastdrags.com/fast-rules It gets expensive to run that fast. Vewwy, vewwy expensive.
Bring all you got.... and hope you brought enough.