So you need to re-develop the maps without requirements from the business? At some point, you will have to have the business users sign off on your design.
If this is the case, you probably need more info than you can gleen from wmusers.com. UCCnet has been a moving target for years. For example, their RCIR has gone from a one-key design (GTIN was the unique key value), to a three-key design (GLN, GTIN, and target market make a unique RCIR).
The only way to come up with a good implementation design is to have a solid grasp of UCCnet. In my opinion, this domain knowledge should belong to a business person, not someone developing Flow.
Sounds like you are a consultant when you mention your client. Make sure your SOW starts at the right place. Either your client will provide you with requirements from which you can re-develop the mappings, or your SOW begins with helping your client understand v3.0 of UCCnet. If the latter is true, have your client pick an internal champion. Have your client pay for training for you and the champion.
This is a lot more than a re-mapping project.