Almost useless rambling and a few questions: Ok, I pulled the motor from my 1989 C1500 to put in my 1979 K20 and there are way more wires than I thought! There are two groups of wires that come through the firewall: one on the passenger side and one on the driver side, and they both connect behind the engine near the distributor. I guess I need to take them apart and see what wires do what? Do I still use the current starter circuit for the K20? And the K20 alternator wires? The wiring harness on the passenger side came through the firewall and went to the computer and also had two other connectors that went under the dash. It looked like one went to the driver side and the other to the heater/AC fan, they are circled in red and yellow in the pic, what are they? Do I need to take out the diagnostic port thing from the donor truck? What do I use for a check engine light? If you're still reading, sorry for so many questions. I am really lost on this and don't want to screw it up.