340 intake
Aug 1967 would not be out of line for a Jan 68....
68 being the first year of the 340 many parts would have a cast date in 67 as they were gearing up for production.
You may get one closer... Oct/Nov 67 if you keep looking, but most would say Aug is ok too.
From what I have seen.... The range in correct dates is a bit wider for Mopars than some other brands.
For example on a Chev it was 1 or 2 months normally.