My Reality Check Bounced
In my 2011 parts book, there is only one master cylinder part number. There are a couple more ABS control unit part numbers than can be explained by left/right hand drive, however. None are coded BR1, BR6 or BRY, so probably nothing to do with HD brakes.
2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6, 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac