Topic: 78 Head date codes

[safariwagon]

I have a 78 WS6 Pontiac 400 with a casting date of K087.  I believe that is November 8th 1977.  I have read all 400 Potiac motors for 78 and 79 were cast up until Nov. of 1977.  The delivery dateof the car was 6-24-1978.  The trim tag says 6DU - - 211617 on the build date line from what I can tell.  There may be a zero before the 6 partially covered by the screw.  It had 70 GTO #13 heads on it.  I am trying to locate some 6X heas that are close to date code correct.  But would that be like a May-June 78 casting date or would it more closely match the Block casting date?

[4SPEED]

form what I've seen the heads can be up to 5-6 days older then the block date. never after the block date. (that I've seen)
and have seen the heads have the same date or be 2-3 days apart.