This crank needs a bottom bracket bearings with inner diameter of 24mm bearing on the drive side and 22mm on the non drive. These inner diameters corresponding to the crankshaft diameter. The bottom bracket bearings can screw into the 68BSA shell on either side.
The actual outer diameter of the bearings is 37mm. Such a big diameter is possible because the bearings are outboard. If the bearings had to go inside the shell, they would be limited to 34.92mm, which is the inner diameter of BSA threaded shell. (1.375in (34.92mm) x 24 TPI)