The plate in question was made to accommodate a CAT TC88 if symmetrical, or TC99 if not. They are long out of production. (1986) The Comet and Comet clones from China are wider, and that is why we need to trim the plate on several bike models.
Trimming the plate is not that difficult, and by doing so, you immediately remove the headache of finding a vintage torque converter that needs to be rebuilt anyway.
You could modify the TC driver to adapt from 5/8 to the new 3/4 with shims, as Comet did this during the transition from the 88/99 series to the 20/30 series.
Here's a TC88 (symmetrical) on Ebay. They don't come up that often.
https://www.ebay.com/itm/Comet-TC88...319?_trksid=p2349526.m4383.l4275.c10#viTabs_0