<<However, regarding the stamping thread, perhaps John was meaning that the engine code was stamped long before painting, perhaps before assembly of the block even began.
After the long motor was assembled, the pad was masked and the motor painted - off it goes to Chevrolet.
The partial vin was then stamped at the start of the Chevrolet engine dress line to an already painted engine, with no paint on the pad.
But I surmise, we need John to guide us to the light. >>
At the engine plant, stamping the pad was just about the last operation on the engine assembly line, done after the heads were installed (except on Tonawanda big-blocks, which were stamped BEFORE the heads went on). The only I.D. on the engine when it started down the line was the suffix, scrawled with a paint stick on the side of the upside-down block; that's what told the line workers what innards to install in the block.
After the pad was stamped and assembly was completed, the engiine was painted (with the pad masked) and shipped to the assembly plants, three engines to a rack. The partial VIN was stamped on the pad at the car assembly plant (from the Chassis Broadcast Copy) shortly after the engine was hung on the Engine Dress Line conveyor.
Photo below shows the typical "bare-naked" Chevy V-8 on the shipping dock at Flint V-8; photo was taken in 1955, but it looked the same through the mid-70's; everything you don't see was added at the car assembly plant.