I've had these on my '73 Dart with 1" Torsionbars.
Over the course of some 4 years of daily driving I found I had to increase the rebound-setting every now and then to keep the shock in it's performance range.
After that time the shocks were maxed out and started to decline in performance.

I upgraded to a 1.08" torsion bar and double adjustable Viking shocks at the front now. I like the seperate adjustability of the compression and rebound on these.

I still have a pair of single adj. QA1 shocks on the rearaxle w/ 7 blades per leafspring pack per side. Installed these in the same year as the Hotchkis/Fox shocks. But I can't help but to think the QA1 shocks are holding their setting way way longer than the Hotchkis/Fox did....