Sway bars?

I've used Addco's rear bar on a Nova I used to have, the Demon has a PST unit. Pro: Reduced understeer. Con: Increase unsprung weight.
What it means to drive it. Reducing understeer makes the car feel more balanced in the turn. Both times I used the biggest bar I could get. This has allowed me some power oversteer without resorting to steering and braking tricks to get the tail to hang out a little when cruising briskly.
Both the Addco and the PST bars mount to the axle using their intended mounting method. This increases unsprung weight. Know how the car likes to hop sideways going over some kinds of bumps? Increasing unsprung weight increases this tendency. I've fabricated brackets for the rear and mount the bar to the body as the old Dart cop car did. In this way, the bar is carried by the springs. This does not make the car quit wanting to hop sideways, it just doesn't make it more prone to do so.
The bars in the auction look like they'll fit your 73 K-frame and axle combination. Good luck.