After the battery, I'd check the starter itself. The hot cables could be an indication the starter is seized. Check all connections to the starter as well.

Reconsidered after thinking about it a few minutes. You're dealing with lots of unknowns on a truck you got from the CU. I think before I went after the starter that I'd pull the spark plugs and work at getting it turned over that way. PO let the oil get down, fuel issues and who knows how long its set since it last ran. You may have fluids in cylinders or even corrosion issues. My approach would be slow and persistent. YMMV

 

I agree with the previous post, you do need to determine if the engine is seized before trying to start it again. The battery cables would not be hot unless there is a lot of current going to the starter. That heat probably means that all the control function between the start switch and the starter is working properly and the starter is pulling too many amps.
This probably is caused by a "Locked Rotor" condition which means the starter can't rotate, the starter could be the problem but I really think it is more likely an engine problem.
Remove and inspect the sparkplugs looking for water or rust. If they are ok before reinstalling the plugs try to rotate the crank using a suitable socket and breaker bar on the damper bolt. If it isn't frozen and turns ok then remove and check the starter. If it is frozen then it's time to drop the pan & find out why.
Good Luck!

 

Check the ground wire. Follow the negative battery cable and make sure it's not loose wherever it's bolted. Then follow the positive cable and make sure it's tight where it's bolted to the starter. You said you changed the battery because it wouldn't hold a charge. That means that everything was working, but the battery was the problem. I think in changing out the battery, you somehow moved the cables around enough to worsen an already loose connecting on the other end of the battery cables.
Good luck and let us know what you find.

 

I haven't had time to do much but I did have the truck towed to my house so I can work on it. Wires look good from what I can tell.
I added a quart of oil because I couldn't tell how low it was, now it is a little over the full mark, but since it hasn't been cranked, I'm thinking if it cranked and ran a minute the level would drop down a little most likely.(?)
This is a short video I made this morning showing what it sounds like when the key is turned. From the inside it sounds like a clunk, but with the hood up I hear a little spin after the key is released I think, see what you think from the sound. I don't see any movement at all in the belt or anywhere.

https://drive.google.com/file/d/1HKN63mqpVbdWWoB_7EvHXnTTjpDKBeSH/view?usp=sharing

 

It does sound like the starter. I would try removing all the spark plugs and trying to start it with them off and also turning it by hand from the crank bolt to see how it feels. Second would be taking off the starter and getting it checked at an auto parts. It will take some time since you have to remove the intake manifold. I would also recommend checking your valve cover gasket for any leaks and replace it, while you have the intake manifold off.

 

I'd hook jumper cables to a known good battery and then to the main terminal on the starter the other cable to a good ground and then turn the key to see if the starter spins. That will eliminate all potential electrical issues before you go to the trouble of replacing the starter. I'd agree with removing plugs and trying to turn the motor at the bottom crank pulley.
Let us know how it goes.

 

I think you should quit trying to have the battery blow up in your face and make sure the engine isn't seized before you do anything else.

 

OK, I put marvel mystery oil in all the cylinders a couple months ago, and tried every week or so to turn it over and got no results. A guy asked if I wanted to sell it last weekend and I figured what the heck if I can get most of my money back out of this clunker that would be great. Tried again yesterday, nothing. Tried this morning, bada bing bada boom, it's turning over! wiz, wiz wiz, round and round, no taps or clunks.
Think it's safe to flush out old oil, put in new oil, and spark plugs and try to start it up?

I didn't agree to sell it yet, that would suck if he had put the key in after I sold it and it turned over!

 

Crank it w/o the plugs installed to blow out the Marvel oil, install the plugs and try it. Cover the plug holes w/ an old towel or big rag to keep the oil from blowing everywhere. You have nothing to loose and maybe you will gain a useable or sellable truck.
Good Luck

 

I already blew a good bit (all over the place) turning it over this morning but good idea about the rag.