One place to be sure and protect is the front cab support box.
That oval plug by your feet on both sides.
Once the cancer starts in there it's 85% terminal.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.