A cargo carrier kit for a truck comprises a plurality of first rail sections for joining end to end to provide a first side rail. The cargo carrier also includes a plurality of second rail sections for joining end to end to provide a second side rail having a separation from the first side rail and a parallel relationship thereto. A forward load bar, supportable on the first side rail and the second side rail provides a connection over the cab of the truck, between the side rails. The cargo carrier kit also includes mounting blocks for releasable attachment of at least a first load bar and at least a second load bar to provide cross members connecting the side rails and positioning the first and second load bars respectively over the mid-section and rear of the truck bed.