I'll throw my guess in here. If it was near the end of the 1970 model year and there were sufficient assembled engines in stock to fill the remaining 1970 orders (or close to it), rather than shut the engine plant down for two months they simply started building engines for the 1971 model year even though it hadn't started. As it appears the engine sat in stock for nearly a year before being used tells me that demand for the 440 was falling OR it was a victim of FILO inventory. Which brings up another topic. There have been numerous posts on how to preserve an assembled engine for long term storage. I wonder how the assembly plants handled this?