the aftermarket harness's like ur talking about are a waste of time. i jsut started doing the wiring for my truck tonight and shit...i dind't know anything about the harness or nething but figured out whut needed to be done by jsut plugging evreything in and takin out shit like emissions and a/c, lights, shit thats not connected to the computer. and then just use the truck shit from there, the oil pressure, the temp...evreything. and same wit the truck harness, get rid of smog and all the shit for the old engine(unless its on the new one). and the problem with settint he engine foward is whut determines whut kind of fan you can use and possible if u can have a/c or not.