I thought I read somewhere that all "I's" are to be read as ones.
Of course I can't find that quote today.
Look at the bottom of this page from the Keith Hardy site.
http://chevy.tocmp.com/models/engine.htm In 57' the engine code changes to:
Engine plant, month, day, type.
So using the info from the above site for 1957, your engine code would be
F = Flint plant
10 = October
22 = 22nd of month
A = regular 235
I'm not sure in how many other years the "A" suffix was used to designate 235's.
Hope this helps.
