The Central had the second largest freight car roster in North America, second to only the Pennsy. I dug through my NYC database, mostly gleaned from the NEB&W website (http://railroad.union.rpi.edu), and it appears that MOST of their boxcars were built by Despatch Shops. Here's what I come up with that's positively identified as being built there:
1920 "USRA" all-steel box: 18,000+ cars
1932 ARA boxcar (X29-type): 97000-97099
1932 ARA boxcar (original test car): NYC 100000
1937 AAR boxcar: 157000-158072, built 1942
159000-159999, built 1949
1944 AAR boxcar: 162000-163999, built 1949
172500-173499, built 1951
174000-174999, built 1949 (original Pacemaker cars)
179000-179999, built 1953
42000-43499, built 1956
As I said, these are the only classes that say Despatch Shops. I'm sure there are others, but no builder is identified.