See the PDF link below for installing body mount coupler boxes, new trucks and wheel sets on Bachmann Box cars.
https://images49.fotki.net/v1680/filec91z/a4014/4/4125954/16375553/RetruckingBachmannBoxcars001.pdf (https://images49.fotki.net/v1680/filec91z/a4014/4/4125954/16375553/RetruckingBachmannBoxcars001.pdf)
(https://images15.fotki.net/v1685/filePvgv/a4014/4/4125954/16375553/Bachmanncoupler.jpg)