So the conversion is a bit more intricate than just throwing a rack back there.

The WHOLE subframe is different. NON 4WAS do not have the mounting bosses for the rack and adding them well...... you're talking about perfectly setting up a rack, measuring, welding mounts and pray for the best?
Hypothetically you'll need the whole subframe.
Wiring is part of the rear harness.
The front column is 4WAS specific. It uses a variable ratio decide what ratio the front needs to have to match the rear.
Uses a 4WAS control unit that needs to connect to the CAN bus

In other words, not to disrespect but nobody is doing this swap anytime soon.

My suggestions is to find a person that has a 4WAS G37 and ask to drive it and decide if it's worth it for you and then aim to buy one. Honestly.