These headers will fit a van.
Hedman Headers There is a ceramic coated version as well, twice as expensive but would be much more durable.
Any headers you'll need to have a Y-pipe made (the stock y-pipe is actually horribly restrictive, you want to ditch that!), and new pipe and muffler back from that. Any exhaust shop can handle that.
I've considered for my van having a new exhaust made using the stock manifolds so I can keep noise down, new y-pipe and a 2 1/2" pipe instead of the stock 2 1/4". I feel like this would be nice from a noise standpoint, and the pipe would not be so large as to reduce back pressure and torque, while still adding a bit to the top end.
Cheers,
- Rich