Wondering if the 67 5 E is julian date March 8 or year 1967?
If it follows other patterns we see on these springs it would be the julian date making this March 8 1965
As you mentioned in your first post we would expect to see the Ford engineering numbers with either supplier during this period of time.
Shape of the leaves would also possibly support (or not given the time period) them being aftermarket
Just one more thing to check.