The "F605A" decodes as F = Flint assembly plant, 6 = June (6th month), 05 = 5th day of June, A = Regular production 235 passenger car equipped with 3 speed or OD transmission. The previously decoded "casting date code" is what would make this a 1958 engine. My comment above about the casting number 3738307 being "truck" specific is incorrect as that is in a different resource I just checked indicated being used in 1958-62, but did not specify truck only. Sorry if the earlier info may have misled. It has been corrected.
