I am sure you have done the usual Google routine.....unfortunately, Mr. Donahue is no longer with us. There should be a way to find either a TransAm AMC person or a factory AMC engine engineer....maybe the Trans AM engine builders. TRACO built the Chev engines in Mark Donahue's cars...who built the AMC engines? Wally Booth had an AMC pro Stocker as I remember....maybe there is a connection there with someone who can direct you to a person who was there and touched the stuff in the day. The low deck AMC stuff has got to be ultra rare....in the old days, we only looked for block castings with 401 on their sides to put in jeeps.