August 31, 1956 is the date the factory shut the 56 production line down to re-tool for the 57 model year. The production line was shut down for 30 days, until October 1 or thereabouts, for the retooling. So if that block was cast September 26, 1956, that would make that block a very early 57 block. A look at the vin plate and a little deciphering might tell you when the truck was built. Anytime near the first couple of weeks in October 56, and pretty good inference that the block and the truck are original to each other.
As another example, I have an 848 head with a casting date of September 55. But the 848 head did not enter service until the 56 model year so its a very early 56 head, same as the above block
As for Special, I have never seen that on a block before. Very very interesting.
Last edited by Dragsix; 11/10/2023 2:46 PM.
