Need help troubleshooting electrical problem

[stock75]

Hello everyone, haven’t posted in a long time but that hasn’t stopped me from combing the forums any time I have a question or problem. After spending some time searching to no avail I was hoping you could help me diagnose my problem. Vehicle is a 84 jimmy. Fairly sure this came stock with a 305 but was swapped to the 350 at some point before I got it. I was going to a relaxing drive with my dog a couple nights ago and all was well then all of the sudden I lost all throttle response and heard an extremely large backfire. I was able to coast into a parking lot luckily. Once I got to a safe place to trouble shoot (vehicle was still running) I came to a complete stop, found neutral and tried revving it up to clear it out as before this happened I had been idling while taking a phone call and when I’m out wheeling it has been known to load up from time to time. So I tried revving it up and got absolutely nothing, it was still running but just barely. So I turned the ignition off and popped the hood to see if anything obvious was wrong. Everything looked fine so I moved to the fuses, I happened to have a volt meter on me and checked all the fuses for continuity, all of the fuses were fine. At this point I tried starting it up again. Turned the key and got absolutely nothing. Checked all the wires going to the starter as well as just an overall quick wire check. Everything seemed fine so I tried having someone jump me. Even with the other vehicle hooked up via jumpers I got absolutely nothing when turning the key. I got towed home and it sat for a couple days until I had time to work on it. So today i did some voltage checks and more continuity checks in various wires, everything seems fine. I have voltage on the wires going to the starter which leads me to believe it might be something with the ignition. The headlights,, tail lights, and dome light seem to be the only circuits that are functioning. While I have a solid 12 volts at the starter terminals it will not even attempt to crank. None of the gauges do anything when I turn the key to the on or acc position either. Also the blower motor is not working at all. I am a high voltage lineman by trade but when it comes to these car circuits I’m like a fish out of water. So where should I start as far as trouble shooting goes? I also found it weird that while I am getting voltage to the wires where they connect to the starter, the bulk head on the firewall is not giving me any reading. Thanks In advance for any input!
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