Attached is a pic with some text. I think I am simply miss understanding. I tried searching "T90", Bearing Adaptor Plate", "Main Shaft" and other key words but I have not found any info. The t90 rebuilt sheet on this site has been very helpful and it makes a comment about the "Large hole" adaptor plate vs. the "Small Hole" adaptor plate but does not provide much detail.
Any help is very appricated. Thanks.