Karen Nakamura has put together a review of the Mamiya RB67 Pro. It goes into some fine detail on the history of model, which was first introduced in 1970, with substantial improvements over the past 30 years.
Nakamura explains modifications she’s done to her RB Pro, including mounting an RZ waist level finder on it, “which confuses everybody,” she writes. She warns you won’t be able to use your RB hood after this conversion without replacing the screws a second time. She also reports this modification is physical, and there are no working electronics between her RB body and the RZ hood.
The review also contains interesting sections on lenses and an auxiliary handle.
You can see more of Karen Nakamura’s work at photoethnography.com.