B737RE Fan Diameter

The efficiency (SFC) of the LEAP engine for the B737RE (I call it the LEAP-2B as I think it needs a different, aka smaller core) very much depends on the fan diameter, as with a larger fan you can have a higher bypass ratio, enabling a smaller Fan Pressure Ratio (FPR), which translates in a higher propulsive efficiency.
For now there are four fan sizes in discussion, reportedly ranging from 63" to 70". The lower end represents