So, to summarize, the 1980 and 81 harnesses are each totally uniquie. The 1977-79 harnesses are more similar, but on closer inspection the IP harness is different for each year that I am trying cover. Arrangement of Wiring Under the Dash Before I go on to the individual options, I think a little illustration is in order to kind of get the lay of the land. Shown below is a 1977 I.P. harness that is off the car, but arranged as if it was hanging on the inside of the firewall. read more