Several different things can caused the thrust bearing to wear out, one is the converter being ballooned, another is not enough clearance on the converter to the flexplate to start with and possibly several others that I can't remember right now. The fix is to have the thrust surface welded and repaired or replace the crankshaft
We use to have a bad thrust surface hard chromed but a lot of that went away when the crazy enviormentalist got thier way with the local goverment agencys shutting the local chrome shops down