I think the c50 is in the 1.5T category, the c60 is a 2T, but as Steve sez that terminology is misleading, and the actual GVW rating varies with wheel and tire sizes ... w/ an empty weight of 9000 and a GVW of 16000, you should be able to carry 7000# legally, as the registered GVW is the max allowed by the DMV, and when new the truck would be warranteed to the 16000 GVW, damages or accidents resulting from weights beyond that are your fault ....
the GCW of 26000 means when the truck is loaded, you can pull a trailer with a gross weight of 10000, again legally, and to be within the OEM limits
I've regularly carry over a ton of apples on my 1/2T long box, w/ a GVW of about 4500 I think, and an actual weight of 3500, according to the title
Bill
