Those pieces do look like brazing that peeled off don't you think?I would have to agree with the driveline shop and the info they shared with you.
There is no bushing or washer in that converter and the only bronze would be from brazing the fins if the builder made that type of upgrade.
I am out of town till next week but we can cut your converter open and inspect it in our converter shop. Hit me up next week if we can help.
