Intermittently bucks and goes dead. Sometimes it won't start back for a few min.

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Started out going dead but would crank right up. Then I had to switch from rear to front tank and it would fire right up and go dead when I put it into gear but when I switched back to the rear tank it ran fine for a while. Replaced fuel tank and pump. No change. Kept getting worse having to turn it over and over and over before it would crank. Finally died and had towed to mechanic. Replaced distributor and ran fine for about three weeks and started again. Replaced distributor again. Immediately went dead. Then it bucks as if though losing fire. Fuel pressure remains constant when it dies. After it has a bucking fit and I make it home, it cranks and runs fine for about 70 miles and starts bucking. Sometimes I can disconnect the positive cable for a minute then put it back on and it cranks up and runs fine for a while. Things that I have replaced, battery cable ends, fuel tank selector switch, ignition control module, computer, idle air control valve, batter cable ends. Still intermittently and violently bucks and dies. I have the dash board completely torn apart looking for a short in the wiring on the firewall. I would appreciate any suggestions as I the truck has spent more than ten weeks several different shops and I simply cannot get it figured out. I have only managed to get it to act up in front of a mechanic one time who said he was going to run some tests in the morning but again, it cranks right up and drives fine when it is cold so no dice. The truck is not throwing any codes either. Thanks in advance.