86 F-150 8cyl/auto with bastardized ignition system. EEC-IV out, GM HEI in. Starter stays engaged after starting. Alternator 65 amp Motorcraft w/internal voltage regulator. Right now I cannot connect battery as the negative terminal end arcs like a bloody welder when contact is made with negative battery post. Alternator, starter, start solenoid all new and retested. Ignition switch new. Sometimes the cable will simply arc on contact, sometimes the motor will attempt to start without using the ignition switch. Losing hope, already wasted too much time on this. Any ideas would be greatly appreciated.