I've got a few helicomatics, and none of them use 1/4 inch bearings. The early rear hubs all use the 5/32 bearings. The fronts use 3/16. The later 700 pro rear hubs use 3/16 as well and have improved cones and labrynth seals.
You will hear that the older rear hubs are junk and not to bother with them.