So the issue with gaps between the head and the bores has been solved. The EvilBay bores are the cause. The original bores fit fine with no gaps.
2nd attempt at re-assembly halted though, due to one of the helicoils failing... caused by a little bit too much torque, due to an oopsy with the torque wrench. Completely my fault.
3rd attempt (and hopefully final assembly) begins tomorrow
So close!!!