I remember back about 1955 when Kadee couplers came out. About the same time the NMRA came out with their stupid design. I couldn't believe what the NMRA did. The Kadees were so slick and looked protypical. Oh, well.
I don't think body mounted Kadees work well on O-31 track. They must have fairly wide radius track. Correct? If I were not a toy train operator, I would consider installing them. The Lionel couplers are OK, but they are not even close to scale. But then, almost nothing is to scale due to space limitations. And 3 rail isn't exactly scale. But 3 rail track and sharp curves and limitations on the amount of track I can fit in a small space doesn't keep me from having a lot of fun with my trains. And fun is the primary objective.