SHA1 hash with custom Characters in it.

[mastercracker]

You are way off. The hash is specific for the word "Book". If you change any character from it, you won't be able to crack it. Your best luck is to find a real hash that already fit the pattern that you are looking for. The 3 sources I can suggest that you look into are Insidepro's forum, MD5dekryptor and Hashes.org. Look in cracked or uncracked SHA-1 (or length 40) lists and find one that fit your need.