JDM ITR, or JDM with auto climate?

as far as i know the autoclimate has to be re wired to work properly in US spec cars. My Audio Guru did an install for a customer of his. he told me it was a nightmare, took well over 6 hours to hook the system up. This same Guru also wired up a 91 Imprezza to WRX spec. he said the only thing that was working at first was the turn signals, everything else had to be re wired to work.