Block difference between 98 and 2000

What are the differences between the blocks on a 98 and 00 block?
1996-99......53020569.............................4883025
2000-01......53010449AA.......................5013166AB

Does it have anthing to do with distributor vs distributorless ignition? In particular the mount for the cam sonsor or distributor? I have searched a little and can't find anything.