The 235 head, 3836848, was used at least 56'-60' I believe.

F121(S),(probably a 5)JC decodes as a Flint engine built on Dec 15.
The engine serial number suffix 'JC' appears in a 58' and 59' list of GM engine suffixes and was a Thriftmaster "235" with 3 speed transmission.

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