The nyloc or plastic insert locknuts are not well suited for the converter. The heat transfers , melts the plastic and they are no longer a lock nut. Use the swedged steel lock nuts would be my suggestion. I use a grade 8bolt with enough shoulder so the threads are not in the bore of the holes. RM
Gr8 fine thread bolts with a precision ground washer against the head of the bolt. Then use another precision washer then a stover C nut and assemble with oil on the converter side. Then you can check the torque after the first few passes and tighten them, after a few retorques they will stay tight. If you use loctite you will not be able to tell if they are coming loose (false sense of tight) unless you break the loctite first.