I like these cars overall. I wish they came with metal wheels and even metal trucks. I added a new set of KD RB trucks to one last week.
I had an extra set of Aristo RB trucks laying here. So I installed bearings inside and then added new larger wheels.
http://www.thetraindepartment.com/wheels-truescale/
The KD 908 medium offset couplers fit without cutting much of the underframe.