Enlargement of the bolt holes means the head would not be in the correct place. That is a problem. Jim's heads are designed with a protrusion to fit in the jug and be centered by the head bolt holes. Even taking Jim's heads designed for the pk 80 and not having that centering feature would be a problem according to Jim. So I seriously doubt this Puch head would work. But hey maybe someone who has done it can report back.
As long as the bolt pattern is EXACTLY the same AND the dome of the head doesn't extend past the edge of the cylinder, THEN you COULD ream out the bolt holes and mount the head IF you wanted to EXPERIMENT with that.