Would not all the small blocks (stock) torsion bars be the same Dia., being they are like a spring that holds the car up from the ground. Using the 6 cyl. torsion bars on a small block, being lighter would transfer the weight of the car to the rear wheels quicker, as the small block torsion bars would do the same for the big blocks. I would only change them for drag racing only, as others have stated. Note: Be careful not to nick or scrape the bars upon replacing. They have been known to break if doing so. Someone mentioned adjusting the torsion bars down for racing, but I believe that will only drop the front end and not give you the transfer needed, being still a heavy bar. In my photo I have SS springs in a mostly stock 69 Dart and when I get the itch with the 4-speed hitting hard, there is no fighting the steering wheel, but just a solid straight line of travel. It all depends on the application that is wanted. One, does not fit all!!!!!