[Mr70]

sixbrl440
That would probably be October,1956.See below.

drdave
Those 515's were used on many,many mid 60's to early 70's GM vehicles,including utility trucks.Just too many to list from 1967-72.
Your format is typical and is dated 1970,December.
Delco-Remy avoided using the letter I in their date coding format,as it resembled the number one too closely.