Express/G-van rear ends?

[C15_Sierra]

I'm on the hunt for a 3.73 rear end (posi if possible), and I intend to keep my stock 5-lug pattern. Given the lack of 2wd squares still existing up north (in junkyards, that is) I'm on the hunt for a comparable rear end that I'd have to do minimal mods to get fitted. A buddy of mine has a half-ton Express van that's a 5-lug, I'm assuming its 5 on 5? Anyone know if those, as well as earlier G-vans, will fit under our squares?