I need to buy and install a class IV trailer hitch and a 7 pin harness.
Not a whole lot to discuss there. A Class IV hitch
receiver is a standard size & shape, and the weight capacity is pretty much defined by it being Class IV (up to 10,000 lbs). The mounting brackets for the receiver will be unique to the van chassis. Most Class IV receivers are the 2" receiver size, but a few are offered in the 2.5" size. 2" is fine and there are numerous ball mounts available for 2" receivers.
https://www.reese-hitches.com/learning_center/general-towing-classesThe 7-pin trailer connector is also industry-standard, though there may be some differences in how the wires are connected at installation. That's custom to your needs and not an attribute of the connector. There are two basic styles, though, one with blades for the connection and the other with pins. I think the blade type is industry standard for RV trailers.
The type of
ball mount you put in the receiver for trailer-towing has more choices, e.g. weight-distributing (WD) or not, adjustable height, whether it has a a bracket for a friction sway control, the type of WD bar mounts, etc. Those decisions are mostly driven by the size of the trailer and style of the WD if you use that. A subject unto itself, I think.