At this point I want to add some comments, as well as my opinions on this project.
My enthusiasm for the project is driven by a major factor of this turbo, and that is this turbo has a 4-bolt housing with an internal wastegate, which is controlled easily and accurately with inexpensive current boost controllers.
We can and will design, develop and build a downpipe to fit a GN with the 4 bolt housing for the 7670 turbo in a GN.
A header modification is also easily modified for the 7670 turbo keeping it relatively close to the stock location/position.
The installation in my car could be reproduced, but is not planned to be the normal street car version.
The 7870 version I am using will use a 3" air inlet, not a bulky 4" pipe which will not affect performance as the inducer is smaller than 3".
Performance is a major goal in our projects, but "simplicity" is also a major concern for fabrication, installation, removal and reliability, and of course "budget" needs to be controlled as well!