I scored on a 14 Bolt from a military surplus lot for $450. It's in great shape with 4:56 gears and a Detroit locker. I bought the disc brake conversion kit that uses GM truck front rotors.
I needed to re-gear anyway (35" tires), and a strong locker isn't going to hurt. Plus, that axle is a full floater so if I do break an axle shaft I can still roll down the road without losing a wheel. This axle is pretty heavy duty.
I'll take some pics...hopefully it fits! The leaf springs are really wide on the van and it might interfere with the brakes. I should know something by the end of the day.