The Lucas catalogs for various years are available online if you search. I believe i posted some links previously. You can then find the appropriate Lucas part number to help with your searches. The wiper arms were available in quite a variety of lengths, bends and finishes.
The wheel boxes were also available with a number of different gear sizes, this will affect the sweep of the individual wiper arms. for example a smaller wheel will give more sweep while a larger wheel will give less sweep. As such it is possible to set up a dual arm set up off the one motor and have different sweeps on each arm.
It is also worth having a look at the control wheels in the motor as these were also available with different offsets/strokes and some even had a reverse park function to them that would pull the arms back downwards to the bottom of the screen in the park position via an eccentric on the drive link that pulls or pushes the shaft a certain direction when going in the opposite direction that it would not normally see during operation.
I had not got around to working out what I was going to use just yet as the Australian design rules specify a certain swept area of the screen. I anticipated that I would have to trial a few different options. I do have two 6WA wiper motors (or were they 6W?). I am trying to add the secondary saturation field (adding a resistor in series with the field coil) to one of them to make it dual speed.
Lucas Master Parts Catalog 400E - 1945-1960 (mgaguru.com)