Have a 1995 K1500. I bought the truck with a bad engine and put a replacement engine in it. The truck started up but would not shut off until I disconnected the battery. The pink wire has power going to the coil all the time. I have unplugged the ignition switch to eliminate that and I still have power at the pink wire as soon as I hook up the battery. Not sure what direction to try next.
the power on the pink wire should only be on with the key in the on, bulb test and start position. If you have power on the pink wire when the ignition switch is turned to the off position then you have a short to power somewhere.
Since you have put a different engine in and have this problem I would look for wires that are plugged in wrong or shorted together.
If you unplug your wire harness from the ignition switch and the pink wire still has battery power then there is definitely a short to power in the wiring