I haven't read the book that Richard recommends but Frank Oddo Knows his flatheads so I'm sure it's a good book.
I have a book called "Rebuilding the famous Ford Flathead" by Ron Bishop. This book covers every aspect of the flathead and even has a chapter on troubleshooting the electrical system. My book has a 1981 copyright date but it's the fifth printing. It's published by Tab books inc. and the price printed on the back cover is $7.95 but it may have gone up since I bought my copy. I think Amazon probably has this book too.