Ground wire burns out on start

[studeclunker]

DANGED computer! Okay, second try here (I need a new computer) we go again.

Okay, every time I attempt a startup, or engage the starter, the 12-gauge wire for body ground burns out. Like instantaneously. The main ground, to block, is fine. Never even heats up. However that may be because it isn't contacting properly.

Now here's the caveat and quid-pro-quo; I was having trouble getting my truck to start off the key and was jumpering it by using a tire iron to jumper across the solenoid terminals.
EDIT:
Eh heh, forgot to say I took the truck to a local pro who will work with me and likes my geriatric cars and trucks. I wanted it properly fixed.

What he did isn't much better as it basically does the same thing with a button on the dash. He cut my new starter harness and inserted a bypass that will engage the starter. I believe the real problem is the Neutral safety switch on the steering column. For that issue anyway.

All of this came to a head when I put a new self-regulated alternator on and replaced the old regulator. THAT mistake is being dealt with in another thread.