BMW had (2) mounting systems (one that had separate left/right pieces just for supporting side panniers, and one
that was all of one piece that combined a small integral rear rack) for the R65/R45 models. These would fit any
bike in the 80-84 range, but the R65LS, because of its wider rear seat cowling and passenger handles, could only use
the separate pieces model as the all-in-one unit wouldn't clear the cowling. Reynolds also sold 1 or 2 models with a swing-back
rear rack that would work on any of the "standard" R65 bikes, but not the LS.
The mounting systems for the bigger bikes R80/R100 are not the same and have slightly different dimensions due to the
taller/longer rear shocks for those frames,and also the front mounting point for them is rotated 90 degrees from that for the R65s.
If one is good with a hacksaw and welder, one of these could be modified to fit R65 bikes in a pinch.