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On 93-95, OPS controls the Lift Pump when engine is running.
So if the part of the OPS that controls the LP (not the same as the gauge) is bad, the engine will not run because the LP is not running.
Careful, this is not quite correct. The engine will typically start and run normally (mostly) even with a dead lift pump, albeit with low injection pump inlet pressure. (Ask me how I know!)

If the OP’s symptoms are no-start, no-smoke, no-glow, the lift pump and OPS are highly unlikely to be the root of the problem.

If you can’t pull codes, something is amiss with the PCM. Wiring/shorts, bad grounds, or malfunctioning PCM would be my prime suspects.

Have you checked ALL your fuses carefully?

As I reread your chronology, two things stood out:

1. The truck was dying under any acceleration and the LP was dead. Yet it was still dying under acceleration after replacing the pump. That’s a little surprising. Did it run long enough to smooth out? In other words, long enough to be sure that any air in the fuel lines was purged?

2. Your bigger problem started after replacing the GPC, right? Which suggests electrical issues, consistent with your unresponsive PCM symptom. So maybe recheck your connections and wiring at the GPC for shorts or other problems?
And check your fuses.

Replacing the ignition switch is not fun.
 
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