I sent my LT1 engine harness to LT1 Wiring to clean it up. they removed all the emissions and anti theft type stuff, put in fan and fuel pump relays and it came back with all the dash wires labeled and ready to hook up. They also reprogrammed the computer. It was about $275 and sure beat the ~$750 a new harness would have cost. I don't have the harness in permantely yet, but everything seems straight forward not to mention I labeled everything before removing it from the camaro (not sure if you had that option). They seem to work with most late model GM harnesses so I recommend them! (someone here, forget who, recommended them to me)

LT1350.com