So far so good.

I ran in the Ford Friction Modifier yesterday for a few minutes on the jackstands and let it sit overnight, per Dr. Diff's recommendation.

I drove it for a brief period this evening starting out with some low speed figure-8's. It clunked a little more on right-hand turns initially but seemed to smooth out by the end of the drive.

I won't be leaving home without friction modifier, synthetic lube or not, lesson learned!