JIS BBs can be had for under $20. Why would you mess with replacing the bearing in one???

Just get a sealed cartridge bottom bracket.

The Shimano UN26 has a plastic left side cup, I would stay away from that. Other than that, most are rebranded and all so close to the same you won't be able to tell the difference.

As PT said, you will have to decide what cranks you will use.......they determine the spindle length.