93 F-150 Electrical Failure

The Vehicle:
-1993 Ford F-150, 6L 4.9L, 5-Speed.
-Previous owner rebuilt the engine, replaced starter, replaced clutch, and installed an aftermarket LED
light bar, klaxon horn, and radio.

The Problem:
-Driving the pickup, I suddenly began to lose power (both electrical and horsepower). Lights dimmed,
engine sputtered. It was almost like I was running out of gas. After several minutes of this, the engine died
and all lights went out. I jumped it, it started/ran fine, then died again in the same manner just minutes
later.

My Response:
-I replaced the alternator brushes and got the battery checked out (AutoZone said it was "Good"). The
problem and symptoms persisted so I bought a new alternator and installed it. The pickup ran without a
problem for two days and then today it again sputtered, dimmed, and lost power before finally dying.
Turning the key gives me "the click". The same symptoms as before.

My Suspicions:
-The aftermarket features are too great an energy drain and they are draining my battery faster than the
alternator can charge it.
-There is some corrosion or poor connection in the wiring harness.
-The previous owner incorrectly installed the starter or went too cheap with the part and it is failing.