There are a bunch of TSB's about popping/creaking noises in turns, over humps or off camber.
Mostly related to loose crossmember rivets.
IIRC the answer is a UHMW slip sheet and drilling/reaming to size for high tension bolts.
Gary has the notices posted somewhere.
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.