Need to determine year of 351W block

Ford uses a part system. To better understand it started in the 40's and continues to today, On all ford vehicles their is a code on every part A=40's, B=50's, C=60's, D=70's, E=80's, F=90's, G=00's, would be printed somewhere on the part. Then followed by the number of the year made for example, if the motor you have had the code E7 as the first two characters it would translate to 87, or F5, would be 95. In your case most ford motors code is on pass. Side part of the motor most likely around the head somewhere toward the back of the motor. I hope this helps.