Swapping couplers on freight cars is usually straightforward. Dealing with locomotives (both steam and diesel) and passenger cars can be a test of one's patience. The issue with steam locomotive pilot couplers is has been addressed to a degree by Sergent Engineering previously with a generic solution. We hope to address this issue more completely in the future by offering pilot coupler retrofit kits for specific locomotives. The issue with otherwise highly detailed diesel and passenger cars is one we have only started to explore.
In general, all these models require something different and we can't address all of them at the same time. Please email us and let us know if you have a particular model you would like to see us address first.