The Stovebolt Site Forums The Shop Area Engine Shop Engine/rocker arm assembly question

Hi all! Asking your indulgence in advance for my ignorance... still learning!

I need the complete rocker arm assembly for a 1955; my question is if I need to limit the search to only that model year, or if the engine changed significantly from prior years.

Serial no. OI535F55Z IIUC, this is a Flint 1955, may have come from an auto, standard trans? I can't figure out the 'OI'. Casting no. 3836233. What model years can I search for rocker arm assemblies? Must be rebuilt. Thanks in advance for any help! The engine now resides in my '50 3100, if that makes a difference.