[JCampbell]

Yeah, I think the crank signal wire grounded out or is broken somewhere. The "pop" I heard when I was testing for crank signal was the fusible link blowing. Replaced the link this afternoon, and decided to test for crank signal a little further "upstream". Grabbed a hold of the harness near the alt to pierce the crank signal wire and the truck fired. Must've moved it enough to restore continuity.

Still need to replace the signal wire, but at least I know what the issue is now.