Truck won’t start and I'm running out of ideas.

No problem .. let us know what you find or if you need more help.. there is relay it should be mounted on the switch panel on the back right side when you flip.it out .. have you checked that out.?

 

That is your main power relay for you cab.. but it feeds power to your key switch and starter button..
I don't belive there are any grounds goining to the relay .. but there is a grounding point on the dash panel close to the relay. but that is mostly for your switches

 

There has been a ton of great information mentioned. One thing I did many years ago, when the starter died, was to remove the power cable from the starter, remove the second nut, push the copper bolt in, turn it 180°, the reassemble. The head of the copper bolt wears out and will not complete the circuit. The starter will still need to be rebuilt, but you can do it another time, if you choose.

 

Now your gonna make me think ...lol .. Iam going off of memory here but I think the power goes to the relay after you turn the key switch on...I'am pretty sure it does

 

I don't belive I would try sand blasting that truck you will end up with warpped everying it's aluminum.. it will look like a wet noodle
Just get some good airplane paint stripper and strip the paint
If you get on YouTube or google stripping paint.on 359 he should pop up and look up Easy Rider and watch his channel he restored a 359 .. he has a segment about stripping paint.. it's helpful and would save me alot.of typing
Twin Sticks Garage is another guy with a YT channel that restored a 359
They are both members here .. they drop by here once in a while