That E278 on the head is the casting date code for that cylinder head (the other head, and the block will have their own casting dates). E=May, 27= 27th day, 8=1968. So those heads were cast on May 27, 1968 --- making them model year 1968, late in the year (the foundry would have started casting for the next model year, 1969, in about June or July of 1968).
The 16 on the head ID's it as a head that was used on 400's and 428's in 1968. It's a D-port head (not Ram Air II - sorry) that should have screw-in rocker studs and "big" valves (2.11 intakes, 1.77 exhausts). For D-port heads, it's one of the better ones.
We still need the date code and casting code off the engine block to ID that.