Ian is probably the only person who actually knows but a friend needs a new big end for his B26 which is ridden almost daily
I had it in the back of my head that the only difference between the two is the B26 uses 12 1/4" x 1/2" rollers while the M20 uses 24 1/4" x 1/4" rollers .
If so I might have a customer for Marks new bearing.
B 65 big end is # 65-486, Alpha B5
M20 is f course 66-545 Alpha B25W

I think I have a nos B26 big end complete with conrod in my stock. I am willing to sell that. Contact me directly if interested. Regards, Bastiaan

email (option): wdmotorcycles@gmail.com

Thanks
I have passed the information on to them
Regards
Trevor