Thats a rig I'd jump all over if I were in the market for a van especially with Weldtec doing 4wd conversions on these now. I'm unsure when they went to the 6 speed transmission but that could easily be gleaned on the the interwebs.
2015 Chevy Express 3500 Duramax
w/ Quigley 4x4 & Agile Fox shocks
Sold 2005 E350 Chateau
Quigley with Agile RIP, 6.0 PSD