'82 E-150 4.9L sat up for months. Turning the key does nothing. Battery & starter both tested good. Replaced battery cables, solenoid & starter coil. Still nothing - not even panel lights!

 

We don't know where this vehicle sat for that period of time.
Could little creatures have made a home and possibly opened one of the fusible links at the starter relay?
There were separate links for lights and fuse panel which supplies ign, it does sound like a possible poor ground coming from the battery to the engine. What cables were replaced ? Was the cable from the negative battery post to the engine replaced or just the two from the battery to the relay and then down to the starter?