Hi,
I have had some recent experience regarding rear wheel bearings.
I bought a new spines rear hub set from JSW that came with a NSK
replacement for the original R & M LDJ 40 bearings.
They lasted something like 500 km,really not up to task at all.
I would advice you to try and get ahold of some original bearings,
Although very difficult to get ahold of I think it will be worth the effort.
The problem with the NSK replacement is that it only has 11 balls per row,
the original ones have 15. Koyo makes a replacement that I haven’t tried,
it has more balls per row but all of the 4 ones I have acquired have a slight
play in them.
Enclosed image shows a not up to the task NSK, a Koyo and an original
Randsome and Marles original type.
Hope that helps.
Jonas