Welcome to the forum.
There is little external identification you can use except - the casting part number which is located on the lower right rear part of the block. You need to remove the starter to get the number. You might try the engine assembly date as a clue. See the first picture. The format is year (single digit number), month (letter, A=Jan, B=Feb, M=Dec), day (one or two numbers for actual date), Inspector code (letter) - 5K26Z. This may help. The second picture is of the casting part number with a similar date code. Tell us what you find and we will attempt to decode it.