If you do install the 255, you will need some installation components:
A new hose to connect the pump to the fuel filter inlet: The stock hose is PTFE and is usually cut off in order to remove. Although someone experienced in using PTFE hoses could probably extract it and re-use it.
A centered fuel pump strainer: The stock one will technically fit the Walbro 255, but it doesnt really hold snug to it.
A method of supporting the fuel pump. The Walbro 255 will not interface the factory fuel pump retaining ring... so you will ultimately end up cutting this ring out. The pump will be pretty loose in there without something to support it. We used to make a billet part for it but now we use fuel pump support foam and it works great and is very easy.
We do have all these items in a single kit just for this exact purpose:
CJM Fuel Pump Install Kit, 370z | CJ Motorsports
Also, someone mentioned possibly having to make other modifications to correct fuel pressure after installing a 255. This is a yes/no/maybe sort of thing. What happens is, the greater amount of fuel that the regulator has to bypass at idle can back up behind the regulator, not allowing it to do its job at idle when the engine is consuming very little fuel. This can cause an idle pressure spike. With a 255, in many cases, the pressure spike at idle wont have a noticeable effect for the owner. Sometimes it will just contribute to taking another crank or so to get the engine started. But the actual Air/Fuel ratio at idle will generally correct itself through o2 sensor feedback.
If you wanted to take the extra step to reduce this effect, the PDF linked earlier in the thread will show you where to drill a part a little bit larger to correct the fuel pressure spike. I would just barely open it up from stock if doing it for a 255.