Any ideas before I start trying to pound on them?[/QUOTE]

Here's what I seemed to dimly remember. I think that there are two different widths for the frame brackets. In the mid 60's there was a recall on all V8 models due to the rubber separating from the steel part of the mounts, and restraints were added to keep the engine in place in the event of failure. The engine mounts were subsequently redesigned with an interlocking feature and the frame bracket width was changed to prevent older, failure prone mounts from being installed. This was in the late 60's. The conflict could be from the difference in those bracket widths. It's been 40 years and the memory ain't what it was, but this info may at least provide a clue.

Bob