Dennis, if your planning on bladder minus the insert, the stock Fox .40 assembly works, this also made available for the MK V. The Fox needle is the one with the oversize knob on it.  A stock OS spraybar for a LA.25-.46 will also work with pressure I'm just not quite certain of it's length in regards to the case. The Super Tiger assembly will also suffice and I have used the Tiger setup many times on the MK III. The III and IV are essentially the same case. If your planning to run with the venturi insert, any needle will pretty much work.