"Can't find the F920H serial number on pad."
You can't find that code on the pad on the block; or, you can't find what that code means?

Yes, 55-57 (all 56-62 235 heads were "848" heads).

F920H would designate:
F = Flint, Michigan Plant
9 = August September
20 = 20th
H = 1957 3100-3800 standard transmission

http://www.1954advance-design.com/chev-specs/1957-t-ser.pdf

If you want to more specifically determine/confirm the year of block/head. fine and post the date casting codes.
http://1954advance-design.com/Web%20images/casting-code-photos/codes-ser-nums.html

Last edited by tclederman; 02/08/2018 12:47 AM. Reason: corrected finger-counting errore
Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.