From what I can find, what you have is a 235 from a '55 First series 3600, Flint plant, manual trans. The head i'm not too sure of. One site I checked showed that head being used from '54-'62. The center bolts on the rocker is one thing that gets me. It's my understanding that all full pressure 235s have the 4 bolt cover, not the center bolt cover. Is there an adapter of some sorts under the cover? I know the make them to put the aluminum covers on the later engines. Perhaps the PO did that to keep the look as original as possible with the full pressure engine.
It seems that you have done well on your research, certainly no harm in double checking.
