Did your truck start up and run before you took the battery out?

Are the terminal posts cleaned/lubed, cables tightened down at each end?
Any damage to either cable?

 

The starter solenoid isn't going to be the problem. If you had power but the starter wouldn't spin over, I would say that maybe it's the solenoid, but with no power, the problem is elsewhere.
If the piece of wire you tested goes to a yellow wire then that wouldn't be the problem either. That's the "hot" to the horn relay.
In the picture of the wires and solenoid, look at the wire that is almost to the battery side terminal, the one wrapped in electrical tape. I have a sneaking suspicion that that is, or was, the fusible link. Unwrap the electrical tape and pull on the wire, see if it stretches.

 

You have a butcher job for wiring , it needs to be sorted properly . But , you need to check for proper grounds also . I see so many get jammed up looking at power + supply only . Grounds are just as important , If not more . Best of luck !

 

Agree with all the above. The starter solenoid has nothing to do with the problem. You need to sort out this butchered wiring hanging by the solenoid and then see where you're at. Mike posted some helpful diagrams.

 

When you start sorting out the wiring, start at the starter solenoid and reference the wiring diagrams that I posted a link to in post #13.
The solenoid and associated wiring is shown on page 2, location C7.

 

And that tape looks much cleaner than anything else around it. Maybe your previous owner "fixed" your fusible link right before you bought it?

 

Mike...I unwrapped the electrical taped wire in question, no fusible link , but the wire is toasted.

Can someone post a picture of restored or stock starter solenoid wiring as a reference?

What do you recommend a complete new wiring harness $700 in NPD or trying to locate a used harness?

 

You need to figure out why the wire toasted, meaning, what else did you do (or not do) when you were working around the battery. Not to mention, if you had this kind of over-current condition in the absence of the fusible link to protect the harness, I'd be concerned of whatever damage may have been done downstream.

 

Here's a stock setup, not a whole lot to see though.
The main part of your problem appears to be a butchered alternator wiring harness, although it looks like some of the main harness might have some damage also.
First picture is solenoid, second is a NOS alternator wiring harness,

 

Double post

 

If you want to do it the really right way, you need to replace the butchered alternator harness.
There are four different possibilities depending on which alternator you have and whether you have warning lights or gauges.
Discounting the 61 amp alternator models, that leaves two possibilities.
Alternator wiring harness
74-76 F100-350 w/ warning lights and 38, 42 or 55 amp alternator
D4TZ-14305-A

Same w/ gauges instead of lights.
D4TZ-14305-B

Green Sales, Cincinnati, OH has 32 of the -A and 6 of the -B parts (800) 543-4959.
There are a few others around, if you want some more names, let me know.

 

Mike your a godsend! I called Green's, I just need to get in the truck and figure out what alternator it currently has (not the original engine).

FMC I am going to check all the fuses tonight, and replace the fried wire with a new fusible link, what should I check next?

 

As long as the rear of your alternator looks like either of these, you should be good to go.
Also, sometimes the amp rating is shown stamped on the alternator.
I think the 61 amp is a large case model and takes a different plug.

 

Mike and fmc400..thank you so much for all your help!!

I spliced in a new fusible link, checked for continuity with my new mutilmeter and POWER IS ON!

I actually sustained unassisted internal combustion for about 30 seconds for the first time since I bought the non-running truck.

 

Congratulations. Fun, ain't it.