Friend’s truck won’t start

This could be a number of issues, wiring faults, wrongly wired, or failure of component, or even just simple bad connection

Pretty difficult at this point

I would start by directly jumpering power to the coil+ and see if you have spark by jumpering the starter solenoid. If not, make sure ignition ECU is getting power. You need a meter or at least a test lamp

With key "in run" but engine stopped, you should have around 6-8V at coil + If you have full battery voltage, the coil is not drawing current, suspect and check coil, or ECU box MAKE CERTAIN ECU box (and VR) ARE GROUNDED. MUSt

Wiggle connectors in/ out, the ECU connector, distributor pickup, and bulkhead connector. Remove connectors and inspect for corrosion, and "work" in/ out several times to "scrub" terminals and "feel" for tightness