Hi again Aleekat,
Maybe Mike is struggling with the same gremlin?

What do you think happened to the negative wire inside that
the solenoid didn't pull in, then after shorting, everything
works for weeks even months? The starter cranks fine so the wires
to the starter carry plenty of current. If the wire craps out
then it might go open I'd think, maybe the trouble is at a ratty crimp
terminal. Did you do an autopsy on the old neg lead?

There's twin negative wires from the battery
One bolts to the frame under the AC plumbing.
The other bolts onto the crossmember under the engine
between the motor mounts.

Just where does the engine block connect electrically
to the negative line? The block is mounted
on motor mounts and there's some smaller ground lines
involved with the Fuel system from the intake manifold to the body,
(They don't look like they return the starter motor current.)
Maybe I'm missing the obvious?

Bill