I've never seen slide-a-links on a car at the track, but I do see quite few with cal-tracs, FWIW. I was definately surprised at how much the cal-tracs helped my car. I had to cut off the shelby underriders I had put on (not fun to cut thru welds laying on my back under the car), and was thinkning the whole time "these things better be worth the effort", the first test drive confirmed that indeed they were worth it. After going to the track and getting them dialed in, I can say with confidence that they are the hot ticket for traction on leaf spring equipped cars. The slide-a-links shoud be effective also due to their similar design, but the cal-tracs appear to be more 'hardcore' so to speak with stronger contruction and the lack of the rubber cushion. I don't know if the slide-a-links come with a spring eye bushing, but the cal-tracs come with a sturdy chunk of machined aluminum. I leave my cal-tracs set for the track, and the rear is stiff, but plenty driveable for the street. I could back off on the preload and soften the rear for more comfy street duty, but then I'd just have to reset them on my next track outting.