If you've ever seen the AtoZ nozzle, it doesn't screw into place, it is pinned to the cylinder. The seal between the two has deteriorated over the replicas lifetime, so I'm giving it a little breath of fresh air. I have the conversion kit, I just need the proper cylinder.
As confirmed by wesley, yes the cylinder head does have threads. At the bottom there's a rubber pad, and around the top of the threads there is a thin o-ring. And I don't mean to thread jack, but where in the world did you manage to find a PAS conversion kit?