My Roadrunner has been 90% street use. Now that I expect MUCH better traction, and it's actually going to stop and steer better than most other classic muscle cars, I'm sure the % of track usage is going to go up.
Although I didn't notice any "signs" that my factory "HD" Roadrunner leaf springs were badly worn out, I had strong suspicion that they were after I bent the heavy duty mounting bracket of Mancini's top of the line adjustable pinion snubber on the FIRST run I made after I installed it. On the 2nd run, it bent more and it was slightly rubbing on my rear diff pinion yoke and had to be removed. If I could only get one of my friends to learn how to shoot video of my car on the launch, I'd have to believe that I would have seen them wrapping up into a S on the launch.
I've had terrible problems with traction on the launch, and right now my Roadrunner is going through a ton of add ons to massively improve traction and all things associated with that, to resolve those issues so I can enjoy going to the track now, and in preparation for a 541 stroker motor I hope to have built and installed by next September 2021.
I got the Calvert split mono leaf springs, and the Calvert sliders, which normally lower the rear by 1/2". As another indication of how worn my factory springs were, the rear rose about 1½" overall!
I'm not sure what your best choices are for your situation, but I got the Calvert split mono leafs and once I had decided not to do a triangulated 4 link rear suspension, there was NO doubt that the Calvert split mono leafs were going to be part of the complete revision of the rear suspension of my Roadrunner.