Is this a symptom of worn out torsion bars?

Well, let's see...
Original stock torsion bars for the slant six power train, ride height as specified in service manual, not sure about origin of new bump stops, and 2-yr old Monroe Monroe-matic shocks.

Other than adding sway bars when able, everything should be equal to or better than stock setup. That's why I questioned the possibility of torsion bars losing a bit of their "spring" as they age, I have heard of a few snapping due to fatigue. And I do know that leaf springs are susceptible to sagging over time and can be re-arched.

Might just go for some heavier duty V8 bars and see what that does.

Jerry