Looks like a suspension lift with blocks and I’d guess some taller coils in the front, not a body lift. You could run a 32” ish tire on that if there is that bit of lift on the front. Boulder Offroad and Weldtec both make 2wd lift kits for GM vans if you do end up needing to raise the front a bit. Something to keep in mind is the offset of your wheels. As Marret mentioned, the tightest clearance will be the front fender wells and too much negative offset will make it even more challenging. I’m running a 285x70x17 as well with a zero offset wheel.
Rears should be no problem.
2015 Chevy Express 3500 Duramax
w/ Quigley 4x4 & Agile Fox shocks
Sold 2005 E350 Chateau
Quigley with Agile RIP, 6.0 PSD