I tried to take a measurement yesterday and got roughly 29" so I will need to check my measurement again.
Finding a long shaft FS5W71B almost impossible since I can't even locate a FS5W71B rebuild kit, but there are plenty of kits for the FS5W71A and FS5W71C. There is another posting saying the FS5W71C's reverse gear kit will work on FS5W71B. I'm thinking replacing my existing transmission's reverse with FS5W71C's parts might be an option worth considering instead of waiting for a FS5W71B to show up in the market.