Jim,
The "R" at the end designates it comes with the retaining ring.
There was a RW507A also made , back in the day, that was used in a Chrysler application. I don't recall the exact one though.
When I restored our first GS, almost 30 years ago, the bearings were starting to get difficult to come up with. I found them at a bearing warehouse in St. Paul, MN. That was where I learned about the Chrysler bearing being the same with the exception being, the Chrysler application did not use a retainer.
Loren