Austin - I can't remember what the OPM is now, I seem to remember hearing that the 50 cycle pulley increased the speed numbers by around 30% +/- but I'm not positive on that...
Mike - Helical drive is simply a shaft that is threaded like a screw or bolt. When motor runs one direction the drive pulley winds up and turns the spin shaft, turning the other direction the pulley winds down the helical 'threads' and drives the agitate/transmission shaft.
I'm thinking Speed Queen probably would tell you they have the longest stroke of all the t/l washers but we've tried to "test" this in the past and found that it wasn't all that accurate.