GCA is the enine serial number preface for a 1949 4000 series truck 216 engine

I found 3835499 as a 1950 head casting code.

Here are locations of head and block casting codes, including date casting codes. Post what you find.

http://www.1954advance-design.com/Web%20images/casting-code-photos/low-press-codes-ser-nums.html