Capelo. As Ted indicated, the oil trough was only used on FoMoCo y-block engines in the U.S. during production years 1954, '55, and '56.
Like the camshaft counterweight that was originally employed, and the rockerarm shaft sheet metal oil baffle trays (intended to deflect excess oil away from the valve stem umbrella seals), the engineers were likely pressured by the cost analyzers and determined that these measures were not necessary. So, in production years 1957 - 1964, these items were removed.
As a hobbyist, I add each of these items to the y-blocks engines I put together for myself or with fellow hobbyists.
Don't lose any sleep in putting your engine together if your engine does not include these items. If all of your clearances, tolerances, and assembly procedures are correct, your engine will give you reliable service and dependability.
Enjoy the fruit of your efforts!
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York