The car we will be working on is an Atlas 100 ton hopper lettered for the Southern Railway. I picked up several of these cars on sale at a local hobby shop a few years ago. Here is the car on my home made test track coupled to the Kadee Height Gauge. I also took the time to put the NMRA weight standards on the wood base for easy reference. At the bottom of the picture is the replacement knuckle coupler and centering spring on the left and a two piece accu-mate coupler on the right.
I could go on and on but the best thing to do for your own fleet is to decide on what couplers you want to use. Scale couples have been in the marketplace for several years now and are getting good reviews. If you are going with Kadee you can use their conversion chart at Kadee.com to see if your equipment is listed.