On mine I used a piece of 3/16 x 0.030(?)" styrene strip. Cut a notch in the body bolster at the right height, cut the strip to fit in the notch, and under the end sill, and glue in place. Drill a hole for the screw and mount your favorite coupler. I used 1025s.
(I think I used 0.030", it may have been 0.040". Use whatever gives the right coupler height. Mine are all old Precision Masters cars!)
Any extra bracing is cosmetic, and can be added as desired.