I painstakingly just finished installing and testing a painless 14 hole generic hot-rod harness in my 78Z/250GTO.I too was new to auto electrics.I can only say work slow, read directions many times.. I installed a vintage' heater only' and the Painless light, wiper, and ignition switches w/ the floor high beam and the OEM turn signal switch. The painless kit does not include grounds, so I ran three ground trees one between the headlights.one inside the rear tail lights and one under the dash from door to door.All exterior or weathered connections I used marine grade shrink-wrap (harbor-freight).I moved the battery inside the drivers rear fender ahead of the antenna.and modified the plastic inner cover to hide it from view and battery posts only on the firewall. To me the unschooled this was a slow painfull job but in the end " to my suprise " it all worked JIM