While at dinner with a few friends, I was asked what position is correct for windshield wipers to “park”.  I said that it depends on the angle of the wiper arms as they lie on the windshield at the “parked” position and that it was easy to reverse.  When we returned to the shop, I did a mini-tech session to show the reversal procedure.
After some research, I’ve found that some MGAs and MGBs park to either side, depending on the angle of the wiper arm.  I had found, quite by accident, that it is relatively easy to reverse the park position within the wiper motor.
Begin by removing the wiper motor from the car and clean the outside for ease of handling and to be able to recognize the parts.  Start disassembly by removing the circlip (see photo 1).  It is possibly the most difficult part of the whole job unless you had to remove the motor from the car.
Next, remove the four screws holding the cover on the other side of the motor.  Remove the horseshoe clip that holds the cable assembly to the gear wheel and remove cable assembly and set aside (see photo 2).  Lift the gear wheel out and notice the plastic button (pointer) inside (see photo 3).  This is the switch that is operated by a cam on the underside of the gear wheel. It keeps power to the motor until the wipers come to the “parked” position then, cuts power.  Notice the cam (pointer); this is the part that activates the switch from the previous photo (see photo 4).
By gripping the gearwheel in one hand and rapping on the end of the center shaft with a small hammer, the gear need only be separated a small distance from the wheel.  Also notice the location of the pin in relationship to the cam (pointer) as well as the square indexing pegs (see photo 5).  Rotate the gear 180-degrees on the wheel and press the gear back into place over the indexing pegs.
Reassembly is as they say, “exact reversal of the disassembly”.  By rotating the gear on the wheel, you have changed the position that the wipers will park from left to right or vice versa (see photo 6).
While this isn’t much use to most enthusiasts (unless they are converting their car to right or left hand drive), it does give a good insight into how BMC/BL suppliers designed parts that could be utilized for different applications instead of requiring a unique part for each, thus saving money.