The date code should be where it's shown circled below. The code on this block is F 18 1
F = June
19 = 19th day of the month
1 = year ending in 1.
You can tell this is a 1961 block because of the road draft tube hole (red arrow), there was no '51 Chevy V8, and the '71 didn't have the road draft hole.
Also it's not unheard of for the date code to be missing altogether. But usually there are enough clues to tell the exact date or darned close to it. In your case, different casting numbers were used during the run of 283 SBC engines, so between the casting number, the suffix code, the aforementioned side mounted motor mount bosses (or the lack of them), rope rear main seal used from 1955-'58, etc., can all help to determine the date it was made.
More on ID'ing Chevy engines here