640 heads

I've been working away on a 640 engine and collecting pieces from a few to make one kinda thing.  When I took the heads off what i think is a 70 engine (no real way to prove it though) they look different than the ones I'm used to.  The "normal" style is rounded and has a fairly deep cavity.  These ones are kind of triangular shape and aren't as deep (1/8").  Is this just the older style or are they something else?  The 4-digit numbers are the same, but the other longer number set is one digit off from the "normal'

"Normal" number on the left:

813065 vs 813165

813060 vs 813160


Normal heads (came from a 71 tnt 640):


This one is another 72/73 nordic Im guessing:



And these are the ones in question:

 

side by side: