I wonder if you drained oil and cleaned area well if JB Weld might hold the stud tight? I have a engine case that had water in it and it corroded the magnesium around the drain plate. Builder that did a line bore and head rebuild said to use JB Weld to make a smooth mounting surface (haven't gotten to it yet).
What's consensus of steel vs billet aluminum sump plate. Seems the aluminum would match the cases expansion characteristics better than steel.