Here is an "alternate" method of mounting the Kadee coupler box/coupler assembly on ANY manyfacturer's car:
1) Use a #44 dril bit to increase the hole sizes on the Kadee box.
2) Drill new a new hole/holes in the PROPER LOCATION (using the Kadee box as a guide/locator) with a #51 drill bit.
3) Using #2 X 1/2" round head stainless steel sheet metal (i.e. self taping) screws from Micro Fasteners (1-800-892-6917), screw the box to the underside of the car. Styrene shim stock from .125" thick up to .250" thick may be required. Simply drill the clearance hole in the shim with the same #44 drill bit.
Finally, for those of you trying to save the $16 for the Kadee "height gauge", DON"T TRY IT!!!! Your dealing with thousands of dollars worth of rolling stock, why skimp on one of the best little modeling aids available? Look carefully at Pete's photo above, and you will see that the rear end of the Kadee gauge even shows how much shim material you will need prior to mounting the coupler! That function alone has been a GREAT help when converting my steam locomotive tenders to Kadee couplers (I use 1/2" wide by .065" thick brass for that).