Welcome to the Bolt.

Your engine serial number decodes as a 1954 Flint engine manufactured for a 3100 with an automatic transmission.

http://chevy.oldcarmanualproject.com/chevyresto/54057.htm

Your cylinder head is listed as a 1956 head here

http://clubs.hemmings.com/clubsites/chevytalk/GMhistory/1916-57cast.html

and as a 1955-57 passenger car head at this site.

http://www.danchuk.com/PDF/Original_Specs.pdf

Someone else can probably clear up any confusion.

Hope this helps

"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson