Electrical failure

[Acoldtruckproject]

So I was in the process of adjusting my carb settings when my engine slowed rpms and proceeeded to die (right when I almost had it down to the correct rpms). I have narrowed it down to an electical short somewhere because when I turn the key nothing happens, even the instrument cluster doesnt come on, and when I go to connect the negative cable to the battery it sparks like there's an active draw. If anyone knows what system/ cable would be most likely to do that I'd appreciate the advice. Also there is a mild leak in the heater core/ hoses in and out and antifreeze was spurting onto the passenger side of the engine, including the starter. At this point I'm not sure what that may cause if anything. Again thanks for any advice.