It does look similar to that plug, but that plug is in the HVAC harness and is not part of the main harness that comes from the bulk head connector on the drivers side like the one I'm trying to figure out. I'll try to get a picture of it before we leave town today.
Barring any major developments or failures elsewhere, I should have the K5 drivable next weekend. Shouldn't take but a couple hours to get everything back on and rebuild the Q-Jet. Looks like I got a pretty good deal in this old thing. It's got a new water pump, belts, hoses, and radiator.