On other engines that have a rocker stud with just an adjusting nut, this can be done a lot easier. But trying to adjust a rocker shaft style rocker like the Stovebolt would be like trying to thread a sewing machine with it running. Hydraulic lifters are designed to have a predetermined amount of pre-load to be considered "in adjustment". You mentioned having several that still click after adjustment, double check to make sure there isn't excessive wear on the rocker pads or worn valve tips that could be causing adjustment issues.
