A friend of mine changed his over to roller bearing by just using the roller bearing hubs and bearings from a s****ped later model. Seems the hubs changed but the spindles stayed the same. I don't know what year hubs he used exactly but I would look for the first series that made the change to roller bearings. What year was that anyway? I know his were early 60's.
Yup, 61-64 full size hubs will work. Use the newer hubs, bearings, races,and seals, with the original spindles and brake drums. The newer dust cap may not go on all the way, but it should go on far enough to stay on. I think that the 55-57 spindle is slightly longer than the 61-64 spindle. This conversion works for 58-60's, also.