The std. shaft B-2's were used in a number of Westminster style clocks. It appears Telechron eventually moved to the higher torque B-3's and B-13's for these style clocks. A B-3 will certainly work but I don't know if it would last any longer. A B-2 may stall out if the movement becomes worn or dirty whereas a B-3 might keep running and the added friction could cause it to wear out faster since it'll stay running under the strain. As long as the clock has performed fine with a B-2 I'd keep it original.
The thick lamination B coils are all pretty much the same and will power B-2, B-3 and B-13. You don't need to change coils going from B-2 to B-3. Just don't use a thin lamination H-3/BF coil. (they won't center the armature disks properly and provide a weaker magnetic force)