Picture of the M75-377 dimensions M48x2mm
This (https://www.bahco.com/int_en/adjustable-pin-wrenches-with-chrome-finish-pb_4307-4310_.html)or two screwdrivers and a bar.
(https://www.sailingmirage.uk/wp-content/uploads/2023/01/New-bearings-simmer-seal-and-rudder-nut-tool-1024x768.jpg)
I used one of these - although mine was pretty loose :-X - good luck!
My write up of our adventure is here: https://www.sailingmirage.uk/blog/seizing-up-rudder-on-passage-how-to-replace-your-rudder-bearings/
I used something like this:
83924.jpg
Not really made for the job, but 'good enough' to get the nut fixed.
My rudder nut is recessed down in the deck fitting so I need the proper tool shown above.
Its on its way to me now as the boat comes out next Wednesday.
IMG_5457.jpeg