I see the confusion. In posts # 10, 12, and 14 you said you had a new heavier wire from the alternator to the pos+ post of the battery which sounded like a replacement charge wire. The next model of alternator has a bolt that the charge wire goes on. That's the bolt I thought you were talking about. So it should have been charging.
Now that you say that it goes to the neg- post I can see it in the picture there - just an auxiliary ground wire.
Now that we've got that bit of confusion out of the way it's more simple - you've just got your charge wire on the wrong post of the solenoid. Move it from the left post to the right one and you should be fine.

 

1995XLT, are you referring to the green wire which I said the three wires from the bottom alternator plug tie into?

 

Yes. It's on the left post, it belongs on the right post. Should solve the problem.

 

Thank you so much, 1995XLT. I am at some sort of public bonfire tonight, but I will switch the wire and report my hopeful success tomorrow.

 

SUCCESS!!! I switched the wire and got a voltage reading of 12.75 at the battery with the truck off, 16.02 at idle!
Thank you so much for your knowledge and patience, 1995XLT.

 

1995XLT...HELP. The success was short-lived. I ran it this morning, but ran the fuel lines dry. After putting petrol in it, it now wants to start, but doesn't turn over. I can hear the fuel pump engaging. It wants to start, but if I step on the gas while the key is turned it dies out.
Does it just take a while for the fuel to work through the line after being run dry?

 

No, it's pretty much instantaneous. I just bought a parts truck on friday that hadn't run for a year - put a battery in it, turned the key and it fired right up.
You will want to maybe get a fuel pressure gauge - it screws on to a schrader valve (bicycle tire valve) on the chrome fuel rail - driver's side of the engine just behind the distributor. A 5.0 requires 30 to 45 psi fuel pressure to run (40 to 45 being what you want to see).
Low pressure could mean a weak pump, clogged fuel filter or a couple other things.
Just for reference - "crank" and "turn over" mean the engine is turning, "start" or "fire up" mean it actually starts to run.

 

Once again, you are a great teacher (and I appreciate your patience with the 'automotivly-challenged').
Would it be easier to replace the fuel filter, or would I be 'shooting rubber bands at the moon'?

 

16 volts is too high! You will boil the battery.

It NEVER hurts to replace the fuel filter - especially if you ran it dry and sucked all that crap from the bottom of the tank through the system.

 

You want to see about 14.5 volts. The integral regulator in the alternator could be faulty.Should be under warranty, don't say anything about the wiring thing.
Fuel filter is always a good idea as glc mentioned, but check the fuel pressure first. You can get a gauge on a loan a tool program but you're almost as far ahead to buy one for $50 - you will use it again, once you know how.
I say check the fuel pressure first because you want to see if that's even an issue or if you should be looking elsewhere.