I upgraded the trucks on my reefer.  I removed the stock trucks and installed Micro-Trains Bettendorf trucks with short extension couplers. (PN# Micro-Trains N 00302021).  I also replaced the plastic wheels, which come stock on the trucks, with BLMA N PN# 9810 33″ precision metal wheels.

Plastic wheels replaced with metal wheels

New Truck with Knuckle Couplers Installed