Truck died on the freeway on-ramp about 2 months ago. I've replaced the battery, spark plugs, distributor cap, ignition coil, and fuel pump. The pump does not prime when key is turned but will prime if the relay is jumped. Fuel gauge reads empty, tank is about ½ full
No spark from ignition coil either

What if you jump the ASD relay and leave all others in place?

no luck

Do you get power to the injectors, or coil at initial key on??

Injectors are getting power, but no power at coil

You only have power for about 3 seconds, unless the PCM sees the engine turning.... Injectors and coil both get power from the same place..... Grab another warm body, have them cycle the key, while you test for power.

The truck still won't start, I just disconnected the battery to attempt something after I reconnected it the check engine light has turned off, however I'm trying to pull diagnostic codes and it's not flashing the check engine light like it should after I turn the key several times. I know that even if there's no code stored it'll flash a 55 telling me that it's done with the check but it's not doing that either

Should flash 12, and 55, if there are no other codes.... if you aren't getting that, try resetting the PCM again....

Makes me wonder if the PCM has died

Your assumption was correct, my PCM had died I just got one from a Pick-A-Part, it starts now, hallelujah, but it won't stay running.