Revised. Had issue with noise that sounded like wheel bearing. 300SD 1985.
Howling noise at 40mph and above. Appeared to come from right front. Sounded louder taking a LEFT turn at 45mph.
Rotated tires , No change.

Found how to test which side has bad bearing. See below. Left front was rough. Right front not rough.
http://www.youtube.com/watch?v=bzB-V8CrSn8
Jack up one front wheel Turn wheel by hand. Feel on spring, sway bar or some suspension part for roughness when turning wheel. Compare with other side. Rough side suggests that is side with bad bearing.

Took both disks and hubs off to examine bearings. Left outer bearing was rough when rotated by hand. But did not appear visually damaged. Left inner bearing rotated smoothly. Rights rotated normally. Replaced only Left outer bearing. Noise gone.

Note Autozone lists genuine Timken 1960 as the oil seal. Part is too large, does not fit. Reused old part. Ordered seal from pelican. Will see if fits.