I used a harness from ken at standalone harness. Its pretty easy. Getting all the gauges to work and have the harness look factory and welding all the old holes in the firewall is the hard partI'm not a big fan of semi rims on trucks, but this thing is sharp as hell.
I'd love to build up a CCSB or CCSB Dually with an LB7 or an LLY, how tedious was all the wiring for the Duramax?