I have a 85 gt with the analog premium sound. The stock speaker harness appears to only have the left front and left rear wires running from the head unit up to i would assume the amp. So when i wire up the new harness, do i only connect those and it will work its magic and everything will work? I have installed a decent amount of stereos in cars and this one is the worst. Getting the stock unit out was damn near impossible! Thanks guys