I think the issue is with the fork and or ball being worn. The clearance setting between the throughout bearing and pressure plate fingers is very small; .06" inch according to the instructions in the link below. With a clearance that tight, any slop/play in the fork would account for the trouble we were having getting it set.
should bring up the installation manual for the Advance Adapters Chevy V8 the Land Cruiser FJ40, H42 4spd Tranny Adapter Bellhousing Kit you have. The instructions do have a specific part number for the pressure plate but I don't know if it cross references to what we used.