Other info I came across.

The older 1927-54 catalog lists the pattern #1 head for 1953.
The other 1927-57 catalog lists the pattern #2 head.

Also, there is a sectional view of the 1953 Powerglide engine in the Motors manual. It featured aluminum pistons.
Is this what they call the "Blue Flame" engine?

Listed as: 6-cylinder 1953-55 engine used with Powerglide, featuring aluminum pistons, full pressure lubrication and hydraulic valve lifters. Also used with standard transmission but without hydraulic valve lifters on 1954-55. The 1956 engine is simular except that a fixed-type, screened oil pump intake, replaces the floating used formerly.

There's a pic & other info listed here.

For sale on ebay 1953 BLOCK NUMBER LAA4I7I23 with head 3701887


-Tom

1950 Chevy 3100 w/ 1956 235