Babbit bearings don't last as long as insert bearings and are difficult and expensive to replace. In fact, there are very few people left that can handle the job.
The dirt particle theory sounds like just a story to me.
I think if you find the bottom end has decent clearances then there is nothing wrong with a rering and valve job for a rarely driven engine to freshen it up. Is there any knocking?

54 3100 with 235
62 flatbed dump C60 with 261