Heres a quote from an interesting article that goes into this a little bit:So, now that we know it's a 69 400, how does that affect value?
"With so many 400 and 455 blocks available, what should Car Craft readers search for when seeking a foundation for their big-cube Pontiac V8 build? We took the question to David Butler of Butler Performance in Lawrenceburg, Tennessee, for his professional opinion. He advises, "With the exception of the mid- to late-1970s PN 500557 casting, we consider all Pontiac 400 blocks functionally identical. The 455 blocks from 1970 to 1976 are also functionally identical. Core shift can vary run to run, so we check every block casting individually before using it in any application, but we have found that no one 400 or 455 block is better than another beyond the well-known issues with the 500557."
Heres the full article:
Not sure if this really answers your question, but it is good reading...