I used the underride bars, welded in on the Deceiver. Hooked up so hard, it broke the front brackets first hard launch! Re-Welded with bracing, no more problems! I used to have slappers in it, but they raised the whole car up. The underrides made the car lift the nose only.
Their greatest attribute being that they allow the suspension to "work" without actually constraining it thru bind. The Cal-Tracs keep the front of the spring from wrapping up and unloading repeatedly, which produces wheel hop, but the front pivot is a rocker assembly that is anchored through the front spring eye bolt and locks against the very front of the spring itself so the system is contained within the spring and thus does not load up the suspension adding spring rate like the original underrider bars do. I have the original underride bars on my Shelby and they bend over time due to the bind they are in and I have to take them off every once in a while and straighten and turn them over. They work quite well but the Cal-Tracs are the Champagne where the Shelby bars are the diet Coke.