Just a quick note that you may want to contact Barry Lowe in Liberty NC. He responds on the Packardinfo site and his contact information should be in the Packard and Classic Car membership books.
Out of his own personal frustrations with what is mentioned in the posts, Barry (who is an machinist and businessman) is preparing to manufacture high speed rear ends for Classic Cars. He also is making other Classic Car parts, which he is already selling. He has purchased the specific manufacturing machining equipment to make the high speed rear ends and already has six orders. Barry owns several Classic Packards, so he is in the hobby and has empathy with our rear end driving limitations.
Robert D Adams
Holly Springs, NC