IIRC, the spark box was a finned aluminum deal; they could be trouble-prone.
I recall replacing one ago on a buddy's '79 Ford Ranchero.
Same symptoms, and I don't recall anything visual like leaked potting material.
"EEC-IV" (IV as in 4) comes to mind...
A LOT of water's passed under the bridge since then, so I could be off on the Gen 4 nomenclature.
Best way to identify the aluminum box type modules is by the color of the plastic where the wires go into the box. Don't let anyone try to sell you a box that has a different color cause it won't have the same plug ins.
