Those are unported race W-2 reads.. the econo W-2 will have a cradle ground in for the rocker
shaft.. forget the number in the inside(oil area).. that is just a casting number.. as to the first
year of the 340.. I THINK that was 67 so that would be a early one
EDIT
I would think those are the long valve version.. which I think all the race versions are.. the econos
have both the long and short versions