I took my Concorde to a front end specialist today after discovering a badly worn and loose inner tie-rod end on the left side which appears to have been the source of the "clunk" I kept on hearing under certain conditions.
The mechanic told me that this is a frequent failure in this car and is almost always the left side. Total repairs including an alignment came to just over $200. I'm very pleased to have this problem behind me as it was a tough one to find. He did check the sway bar mounts and they look good.
Thanks to all for your help and suggestions.
Dave