I had a similar issue in the past.. But in my case it was this with a bad connection (minor corrosion) that would kill the spark, but when wiggled, the truck would start just fine..

BTW, that's one clean engine! Lets see some of the rest of the truck.. welcome to the forum. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Logic says that his is an electrical thermal fault, triggered by a hot soak. Logic is useful, as it is the best way of going wrong with confidence...

You find this kind of fault with something to cool components one at a time. I used to use r12 for this, before it went to $20/lb. r134 will work, too. Tap a can with a valved hose and run the truck up to operating temp, shut it down, and wait until it won't crank, then cool suspected components/connectors until it cranks and do this one at a time until you find it, attempting cranking each time.

I'd try the coil and power transistor and connectors, the doodads in the distributor, the tach connector, the electronic gizmos on the bottom of the coil bracket, and the engine harness connectors at the firewall. ECU last.

I assume you checked the ecu boards for evidence of capacitor leakage and board trace damage?

I haven't read all the posts so if this is duplicate info sorry. My similar problem was the distributer electronics. Cracked circuit board or sensor. Pricey replacement but it fixed my random no start problem.

If its electronic and in the dizzy it is called the crank angle sensor. It ultilizes a special optical based rotor and sensor. This part is pricy and is the only "real" electonic component in the distributer. It is located under the rotor, under the dust cover. I think its commonly called the crank angle sensor, ignition control module, or ignition pickup. Im not familar with testing this piece other then replacing it though, sorry.