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www.bruce-mclaren.com there is a pic of that block there and you can see the same cast number on it in the back, looks like it came out in 67, its sleeved, and should not have a date on it. A GM big block rectangle port nos intake manifold cast for a 4x2 weber 58ida carbs was just on ebay a few weeks ago for 250 and had no bidders, it was a 4/17/67 cast date on top w/ a similiar 0- casting number above it, I would imagine it is the intake that went on that type of block for canam racing, lol
its a 356 alloy, there is a web-page out there for oldsmobile engineered aluminum bigblocks and their descriptions seem similiar to that block, some were dual overhead cam versions, and some w/ true hemi heads and turbos, all were fully developed by 67 and very exotic compared to the zl1 it states but they deep sixed the program, a couple complete motors exist, but none w/ the hemi heads..