I am guessing that the pictured narrow thrust surface is a defect in the original casting/machine work? The ones I've looked at were considerably wider than that one... this may be the larger and more involved problem you have uncovered with that crankshaft.
From looking at the photos in more detail, it would appear that this particular Listeriod manufacturer has carried out a modification to the main bearing journal, by increasing its diameter (Genuine Lister CS engines have a common diameter for the main bearing journal and flywheel mounting diameter.
Whilst increasing the bearing journal diameter is a good idea in principle, it creates other problems:
1), If the manufacture is using a stock blank for the main bearing bush (because if he is not then he will also need a non standard bearing housing), then an increase in journal diameter will consequently reduce the thrust area of the flange, hence the comment above " The ones I've looked at were considerably wider than that one"
2), The internal diameter of the crankshaft timing gear is reduced, hence its ability to maintain an interference fit on the crank journal is reduced, as its reduced thickness now means it is more likely to stretch instead of maintaining an interference fit.
3), The internal diameter of the crankshaft timing gear is reduced, hence in turn as the timing gear forms a thrust face for the main bearing bush flange, so its bearing area is reduced, furthermore if there are any high spots / burrs on the gear teeth. This will rapidly wear the white metal thrust face of the bush even more so. As the lower root portion of the gear teeth will come into contact with the thrust face of the main bearing bush.
All in all another Indian modification which on first thoughs seem to be quite reasonable, but whose knock on effects have not being properly considered.
Edited to correct punctuation mistakes
