For layouts with curves too small for full-length passenger cars, you need SCS's new "Selective Compression" series.
Trucks: Micro Trains 1187 6-wheel passenger trucks without couplers.
Couplers: Micro-Trains #1023
Note: To install the trucks, insert the Micro Trains 6-ribbed bushings into the holes in the raised portions of the floor, then attach the truck to the bushing with the pivot pin, as described in the Micro Trains instructions.
Update: added interior partitions to the shell, to represent the interior walls of the prototype.