Burned hand no more electric

[PKRWUD]

1) Replace the pos. cable with some 2 gauge welding cable.
2) Replace the starter solenoid.
3) Check your fusible links with a DMM set to ohms. There shouldn't be any detectable resistance.
4) Verify your gound connections, and add a ground cable between the engine and the frame, and another between the frame and the firewall (or rear floorpan). The fact that you have the battery mounted in the trunk means that your ground that used to go to the engine is no longer there, unless you've added a cable. This leaves crappy braided ground wires that can't handle heavy loads.

In the future, if you ever encounter a similar situation in which the engine continues to crank over, just rap the solenoid with the handle of a large screwdriver.

Take care,
-Chris