Yes it is all 1 unit.
There is NOT one.
in the fuel tank you can either remove the tank or the bed to gain access.
The 2014 Chevrolet Silverado-1500 runs on flex-fuel (FFV).
The 2010 Chevrolet Silverado-3500HD runs on flex-fuel (FFV).
The 2012 Chevrolet Silverado-3500HD runs on flex-fuel (FFV).
The 2010 Chevrolet Silverado-2500HD runs on flex-fuel (FFV).
The 2013 Chevrolet Silverado-3500HD runs on flex-fuel (unleaded/E85).
The 2014 Chevrolet Silverado-3500HD runs on flex-fuel (unleaded/E85).
The 2012 Chevrolet Silverado-2500HD runs on flex-fuel (unleaded/E85).
The 2013 Chevrolet Silverado-2500HD runs on flex-fuel (unleaded/E85).
The 2014 Chevrolet Silverado-2500HD runs on flex-fuel (unleaded/E85).
22 gal is standard. 34 was available but i believe only with the longbed.