This is a collection of pictures of front blocks to help identify and learn from. If you will notice that some front blocks have a small center hole and some have a large center hole. Up until 2000 all cockers used the smaller center hole and front block screw (banjo bolt). In 2000 the front block banjo bolt was made larger to allow for a larger valve chamber holding area and better air flow to the front block.
Enjoy,
Kmac