I checked the last time I had one of the down pipes off of my van ambulances, and the upper part is exactly the same as the trucks. On trucks the pipe is a little longer, so it would stick down below the frame on a van. All you need to do is get a cheap 4" truck exhaust, and take it to a muffler shop and have them cut and weld a few pieces for you. A truck kit will contain all the parts that you need and a few extras. Unless you have access to a welder your self, then you could do it in your driveway.