Having Problems with engine ID clarifiaction (273 photos)

My friend and I pulled a 273 out of a 66 with the same thing. On one side was a '65 Head with the differnt bolt angle and 5/16 Threaded boltes, and on the other side was a '66 Head with 3/8" threaded bolts and the square angle going into the head. The block is a '66 Block. One side just had a '65 Head on it.

I have another 273 from a '66 and it has the '66 heads on both sides, but it was a spring '66 block, not a fall '65 block.