See if www.mymopar.com has wiring diagrams for that 87 truck. The ign system pretty much just needs (3) things (A) the dist pickup to trip the ECU (we should be OK there) (B) fire to the coil in crank and run (C) fire to the ECU in crank and run. Seperate the bulkhead half & see if the blue wire ign1 (run) circuit has fire with the ign key in "run" and see if the brown wire ign2 "crank" circuit has fire with the key held to "start". This'll direct you to work back inside to the ign sw for the open or downstream on the eng side (likely) to the devices that need to be fed. Pull the yellow wire off of the starter relay so it does not engage the starter till we get it sorted out (no need to run the batt down & we know the starter circuit works).