Hello Jim, it’s definitely been a while!
I had the chance to speak with Pete McCarthy this week and asked him where he located the information on that manifold. He said that when material for the book was being gathered nearly 20 years ago, that was the information he had at that time. As he recalled he had only seen the 485640 available in the parts manual, never on a car. And because it shared the same 485- prefix with many other SD parts, he made the deduction that it was a non-production SD intake. However, we have uncovered much over the past 20 years, including 485640 on so many cars. So that may clear up much of the mystery why Pete’s book says what it does!
Now, we need to determine exactly what is different between the 485640 and the 488945. If there was no difference, it is unlikely that a part number change was necessary. Does anyone have one off a motor that they can take detailed pictures of?
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