m1a2lt,
I began a replacement program to the Kadee couplers as well. Not with the greatest success. The kit built stock I built was able to take the Kadee, and was reasonable generic in the couplers they could take.
I made up the couplers and glued them on. You can screw them on. I bought a coupler guage to ensure the correct hieght and placement. Other stock I just cut the old ones off, and glued the new ones in place, however some of these I had to extend the coupler length, making an unrealist distance between carraiges, and also causing derailments on curves becuase of this. Also some of the existing couplers were "bogie" attached, and I modified the stock to have them "body" attached. Don't do this. alters the line of the couplers on curves, and again, derailments. I also found the kadee couplers tended to sag after a while, and catch on turnouts etc. causeing derailments. I have had to go back and review/reattach/replace most of them. Ones that I cut the old coupler off, I had to replace the bogies. I have now decided to keep the original couplers of pre-made stock, and use kadee on kitbuilt. locos, especially double ended locos, I just have original coupler at one end, and kadee at the other, for dual running. So be careful and accurate.
TOOT!