Went to fire up my car, to see how it ran. But when I attempted to connect up the battery ground cable, major sparking occurred. I have the battery cable grounded to the engine block, and the pigtail lead from the cable grounded to the body. There was also another ground lead, coming from inside the car, going to a strut mount bolt.

All accessories (lights, radio,wipers heater/AC blower fan) are off. What should be checking next? I do have a test light to use

Disconnect the cable at the strut mount.

Is there an audio amp installed somewhere? Big audio amps have large capacitors that need to be recharged and this will actually cause arcing at the battery when connecting.
Maybe a large inverter?

You are drawing excess current from something. Did you hook it up and try starting it?
Need to hook your test light in series with the ground cable. Start pulling fuses or disconnecting things like the alternator and see when the light goes dim.

No inverter or audio amp was found in the car.I did disconnect the strut tower wire, same major arcing issue.

Trying to start it is what I was attempting, but ground cable could not be tightened down due to the arcing

I'm confused about the ground cable coming from inside the car going to the strut....Where inside the car is it coming from? Is this a factory OEM wire, or did someone drill a hole in the firewall and run it? Where is the positive wire for this device? Granted you disconnected the ground from it, but it still may lead us somewhere.

Danged if I know, going to look into it further. A friend gave me a lead on something to look at, will post results when I go out in the morning to work on it

I think your ground cable is live 12 volts. That'* the only thing that fits this.

Problem solved

Care to elaborate.