yes they come as kits. They are all over the internet, but I edited my post earlier-
The biggest discrepancies I've seen are usually how well the plugs work for the factory connector. The ones I've got in my drawer right now (lazy bum never put them on after my latest accident) have a connector almost not at all like the factory one- wrong pin spacing, right shape, wrong latch depth. But I made it work, at least in-hand. The set I had before were perfectly matched. Same brand, same model, 2 years apart.
Anything you order will be manufacture en chine, so they are all the same quality internally. They just put different connectors on them to match the OEM connector.
I had my first set mounded to the front of the core support. Whenever I get the ones installed that I have now, I'll probably mount them to the inside of the frame rails above the steering rack.