Bill's first two books were the better of the three book series. You can still pick them up on Amazon,
Scanner Modification Handbook and
Scanner Modification Handbook Vol 2. I put together several of the mods from these two books, center tuning meter, signal strength meter, 6400 memory mod. It was a lot of fun to do back in the day. Most of the material from the books were written from his monthly newsletter called "World Scanner Report". These aren't available anywhere as far as I know. I only have three years of worth, I think there were seven years total, and they're only hard copies. I've been wanting to digitalize them, but it's too much work.
The third book was geared more towards his computer interface. I bought one of the early kits from him in the early 90's, referred to as the HB232 at the time. It was really nothing more then a glorified keypad emulator. However, it was very handy to use when there was nothing else out there that could auto-program your scanner.
If you're interested,
there is a post from earlier this year by someone that had some circuit boards made up from the book's interface plans.
edit: BTW, I don't think "Off Topic Wireless" is the correct section for this post... just sayin, in case it gets moved, or not...