Simplify the following text for a Grade 4 native English-speaking person.
Original: The XF was developed for the 2000 season to replace the XD , and was chosen as the spec engine for the Champ Car World Series in 2003 .
Simplified: The XF was built for the 2000 season to replace the XD . It was picked as the spec engine for the Champ Car World Series in 2003 .