This will be an unusual conversion for most.
Hopefully i can get some help here.
I have done quite a bit of research in the past few weeks but there is still a few things i need help with.

My vehicle is a 2003 Nissan Elgrand van.
VQ35DE engine with tiptronic transmission.
According to my research these are only rated at 240hp.

My goal is to have at least 400 reliable hp at the wheels.
The easiest way to achieve this is with a turbo.

My understanding is im best not waste my time with the VQ35DE in the van as the rods are not the strongest?

What is a good engine to put in there instead? Engines are plentiful where i live (NZ) and ive been offered a 2009 370z engine. Would this be a good base to turbo? Or should i look for another later model VQ35DE from a skyline or 350z?

Are all the upper intake manifolds interchangeable?
My current VQ35DE has a single throttle with cable control. This manifold fits nicely in the van engine bay and if possible i would like to retain it.

I will be changing the ECE to either a Link or Haltec. What can i do to retain useage of my tiptronic transmission? Can i still get it to operate somewhat? If its a big problem i can fot a manual but i do like the auto.

The van is not road legal and is currently used for track days, burnouts and possibly drifting.

Thank you