All you need to do is count the bolts that hold the rear end plate on the housing.
The rear track of the 2001 Chevrolet Silverado-1500 is 5 ft. 6 in. (66 in.).
The rear track of the 2012 Chevrolet Silverado-1500 is 5 ft. 7 in. (67 in.).
The rear track of the 2014 Chevrolet Silverado-1500 is 5 ft. 7.6 in. (67.6 in.).
The rear track of the 2005 Chevrolet Silverado-1500 is 5 ft. 6 in. (66 in.).
The rear track of the 2011 Chevrolet Silverado-1500 is 5 ft. 7 in. (67 in.).
The rear track of the 2010 Chevrolet Silverado-1500 is 5 ft. 7 in. (67 in.).
The rear track of the 2008 Chevrolet Silverado-1500 is 5 ft. 7 in. (67 in.).
The rear track of the 2013 Chevrolet Silverado-1500 is 5 ft. 7 in. (67 in.).
The rear track of the 2009 Chevrolet Silverado-1500 is 5 ft. 7 in. (67 in.).
The rear track of the 2006 Chevrolet Silverado-1500 is 5 ft. 6 in. (66 in.).
The rear track of the 2003 Chevrolet Silverado-1500 is 5 ft. 6 in. (66 in.).
The rear track of the 2004 Chevrolet Silverado-1500 is 5 ft. 6 in. (66 in.).