The LS7 has not been "picked" as the "racing engine of the year". The LS7.R has been named the "race engine of the year". The LS7.R is not a production engine and mechanically very different from the LS7. The LS7.R is a purpose built racing engine with a designed lifespan of little more than 24 hours. Besides their designations the two engines have very little in common.
Try again.