As for the front seats, the bolt pattern for the base is not the same, what you do is use the original seat bases, take off the seats, the new seats wont fit on the base (there too long) but the bolt width is the same, so you just take some metal rails, bolt those to the base and then mount the seats to the rails. I made a diagram in paint, I hope it helps
If this isn't clean enough I could go take some pictures of my vans setup.EDIT: I was wrong about one little thing, the chairs are wider then the base, not longer











