You can run any engine you want on Lake Shasta. There are currently only about 3-4 lakes that require 4 strokes.  A couple of other lakes require 2 stroke engines that are 2-star emission rated.  There is even one lake that requires not only a 2 star rating, but a gas receit slip from a  Unocal station showing you filled up your boat with Union 76 fuel.  This is because of the formulation that Unocal uses for it's fuel in CA.
Most lakes in CA however, will allow you on the lake with any combustion engine.  They just can't sell engines that are not DFI in CA.