Chevrolet small-block engine
In 1992, GM created a new-generation small-block engine called the "LT1 350", not to be confused with the high-output Generation I LT-1 of the 1970s. It displaced , and was a 2-valve pushrod design. The LT1 used a reverse-flow cooling system which cooled the cylinder heads first, maintaining lower combustion chamber temperatures and allowing the engine to run at a higher compression than its immediate predecessors.
LS based GM small-block engine
Several versions of the LS were used in the Chevrolet Corvette, beginning with the LS1 in 1997 through the LS9 and others in 2013. Variants of the LT version of the GM small-block have been used since. 
The GM Generation I and Generation II (LT) engine families are both derived from the longstanding Chevrolet small block V8. The Generation III small-block V8 was a "clean sheet" design, which replaced the Gen I and Gen II engine families in 2003 and 1996 respectively.