In 1934 the 8 cyl engine had a water side plate cover, used to extract the sand from the casting. This style of block ran to sometime mid to late 1935, when 5 freeze plugs blocks were introduced.
All engine block assemblies carry part # A90458. No other part number has been found for designation of the various types of block.
Five freeze plug engines were superseded by a 3 freeze plug variety which ran until the end of production in 1936, making these rare.
6 cyl engine A90425 started with a water side plate in 1934 and changed in mid 1935 to a 5 freeze plug version.
There are no known 6 cyl 3 freeze plug engines and no change in part number.