So I built a fixie from a pretty old frame and kept the original crank on there. After about 2 months I've decided I'm tired of screwing with the cotters, so I want to upgrade to a new crank. I'm fairly certain that my bottom bracket wouldn't be compatible with any cotterless crank, so I'm looking to replace the bottom bracket along with the crank. I've attached a photo of my current bottom bracket, I'm pretty sure I've got a "loose bearing" style, and I want to know what my options are in terms of replacing it.
Also, would I keep the threaded piece on the left of the photo with the new bb? The right threaded piece is stuck into the frame pretty well so if I can keep those that'd be good.
The crankset I was looking to get recommends a 107-110 mm JIS bb. Any help is well appreciated.