Ah I see. I guess I’m unsure why you want to pursue the AWD van drive train, why not just source HD truck parts? They are going to be more robust, and I’m unsure but probably more common and this most likely less expensive. My van for example uses truck torsion bars, drive shafts, transfer car, and front diff. The main custom parts and the lower control arms and the brackets for attaching. Seems you’d need custom work done for those anyway.
I’m no expert though so do t let me discourage you. I’d love to see you pull something off with a Duramax van. For what it’s worth, I did find out that Hummer H2s are decent for providing some of the needed parts.
2015 Chevy Express 3500 Duramax
w/ Quigley 4x4 & Agile Fox shocks
Sold 2005 E350 Chateau
Quigley with Agile RIP, 6.0 PSD