3769925 (block casting code) = 59-63 261 block
CON3 = engine plant CONveyor #3
C193 (block date casting code)
C = 3 = March
19 = 19th day
3 = 1963 (261s were used in 4x4 trucks in 1963, or, a replacement block)
3836848 = 56-62 235 head
K 2 1 (head date casting code)
K = 11 = November
1 = 1961
"Serial Number flat area is smooth & blank."
Most likely a replacement block (or, a carefully machined-off Engine Serial Number)
This will be corrected by others, if wrong (or, if other guesses seem reasonable).
