What about:

These are used on mid 80's monolever BMW's to fix the final transmission to the single swinging arm.
Thread size is M10, pitch 1.5.
Spanner size is 12mm ring.
So, you might be lucky to drill / tap 3/8 Whit, or remove the existing studs and make new ones with an M10 thread to accept these nuts.
Available here:
https://www.motorworks.co.uk/final-driv ... 789-1.html


