PapaJ,
What do you mean when you say "the casting on the inside of the block is '56.
Are referring to the date code casting?
If so, yes, your block was cast in late 1956 and those blocks were used in 1957 vehicles. If the date code letter is I, J, K, L (Sept thur Dec) the engine would be placed in the next year vehicle.
The stamped pad area is identified in the first line of Randy's posting. The second line with the web site explains it even further. And your eyes "I" are ones "1" which is the month and day.
Block casting 3837004 was used in:
Trucks 1955.2 - 1957 w/ mechanical cam
Passenger 1955 - 1957 w/ hydraulic cam
I have the same block with date code K 3 55. Except the stamped info on the pad has a seven digit serial number and then T56Z. It's a late 1955 block that was used in a 1956 vehicle. This also confirms what Randy said that in 1957 the stamped pad info was changed to plant, month and year and type.
Hope this helps.
