I believe that decodes as: F = Flint, MI 7 = July 22 = 22nd day of that month A (quoting the '58 Chevy Master Parts Catalog) = "Regular '235' -6 cylinder" (with passenger car models listed as original service)
The year was dropped from the later serial numbers from '57 onward, so best indication of year is from the block casting date code located above the starter. This decode is made based on the '58 Chevy Master Parts Catalog, pp 12-14.
Starting with the codes over the starter... you can disregard the CON 4. That just tells what conveyor line was used in the engine foundry.
The digits that follow decode the date as G = July, 17 = 17th day of the month, and 7 = 1957.
That is consistent with the block casting number, since 3837004 was used '55-'57, and it is a 235 as was indicated in the earlier post by the stamped engine number.
Interesting, the head casting 3836850 is a 261 head ('54-'62). Nothing special about that other than it was just a bit lower compression (somewhat larger combustion chamber) compared to the head casting originally used on the '57 235, and has 3 pairs of holes drilled into the water jacket that were needed to properly cool the siamesed cylinders in the 261. They are simply blocked off by the head gasket and 235 block. It's more common to find the standard '57-'62 235 head casting on 261s than the other way around, but there is nothing wrong with that. If you are interested in finding the date code for the head, it is located under the valve cover (valve cover has to come off to see it), driver's side, toward the back.