I’ve done other cars but not K-Lines. My one piece of advice. Start by doing One end of Two different cars. Then run them all over your layout and see how they behave before doing the whole consist.
Are your cars equipped with mounts for them ? Most of my cars are GGD heavyweights. They will make it through an 072 but derail if they enter an 072 off of a straight section. Luckily my layout has easements on all my curves. There are lot’s of variables it seems with passenger cars. Where the truck mounts, body overhang, length of car and pivot points of trucks seem to matter. Putting a 16” baggage car or any head end car with 21” car doesn’t seem to work. The shorter car gets pushed off the rails. Where your cars are all 18”s it will be easier to come up with something.
My go to coupler is an 805 as I have plenty on hand. The 740 is a little more realistic with no exposed spring. The 746 is a longer shanked version with a plastic gearbox. This works well on MTH cars with long diaphragms that are on the stiff side. They also can be mounted further inward in some cases and gain you a bit of coupler swing.
I’d just mount them with just enough to hold them in place and experiment by just pushing or pulling them with your hand through a turn. When your satisfied you can do a permanent solution along with shimming. With passenger cars a lot of variables come into play within the car as well as the cars going through a fixed radius curve off a straight portion.