Latroca', the F56Z engine number suffix IDs the engine as a '56 model year (as Tim said), 235 "regular" 140 HP engine, used in 1500, 2100, and 2400-series cars. The '848 head casting was used from '56 - '62, so a common casting, and considered "desirable" since it has the smallest combustion chamber size of any 235/261 head, for somewhat higher compression ratio (about 8.25:1 as produced, maybe a quarter point higher).
The date codes that Tim mentioned are found as follows: block casting date code is just behind and slightly above the starter. It should have a trailing "5" or "6" digit, since the engine number confirms the '56 model year (production starting in Fall of '55). The head casting date code is under the valve cover, about 2/3s of the way toward the rear of the head, facing the driver's (port) side of the head.
If the head casting date suggests it is a later unit, and perhaps swapped on at some time, it may be important to know, since the rocker assembly oiling scheme changed in '58 and '59. Pre68Dave's blog explains the
235 Rocker Oiling differences well.
Cheers!
Doug
