Motor Mount Adapter to adapt Gen 3 + (99 & newer) engines to Gen 2 (98 & older) and older motor mount systems
These adapter plates convert the "LS" type square bolt pattern back to the 3 bolt Gen II and earlier engine bolt pattern. Basically these allow you to bolt a Gen III (LS1, 5.3L, 6.0L, etc.) and newer GM engine in place of an older one.
These put the back of the engine (where it bolts to the transmission) in exactly the same place as stock so it won't move your drivetrain.
Below are how the adapters should be mounted to keep the motor in the stock location.