My 58 has thrust washers as well. Did the 57 have thrust bearings stock? I didn't think so.
I would probably not redo the second axle, but if you can use the thrust bearings, they are very nice. The thrust washers will work just fine as well though.
What is your use case? If this is going to be a daily driver that you are going to put a ton of miles on, it is probably worth the effort to use the thrust bearings.
