I'm no expert on the subject other then reading up on it. bought a good book by a guy name Bob Bolles, called "Stock Car Suspension Set Ups" that covered this very well, as you have done. There is a lot to be learned IMO before taking on any suspension modifications, there's so much going on...even in a simple leaf spring. One last thing about a leaf spring suspension. Just installing the Shelby type of traction bars is technically turning the rear suspension into a 4 link! just no tunabilty and stuck with what you got.mustangsurfer said:The answer to the question is - it really depends on what you intend to do with the car. Some 4 bar systems are used for different application. And it also depends on if you are talking about a 4 bar vs. a four link. A four link is generally termed for a 4 bar system with parallel bars.
These generally allow for loads of anti-squat, which is why they are used on dragsters.
Most four bar systems have at least one pair of the bars angled to help with locating the axle in the car. They generally use a vertical shock system and when engineered correctly work well as overall suspension designs.
There is nothing inherently wrong with the leaf spring setup. There are companies like Global West who are winning with the old fashioned leaf spring system. A well designed leaf spring setup will beat a poorly designed four bar system all day.
One advantage to the four bar is that you can design it to actually steer the rear axle in a turn. You'll notice that most 4 bar systems have unequal length arms - one set is shorter than the other set. This is because the shorter radius arms will help steer the car in a turn. If you are making a hard left turn, you want the right side of the car to pull the axle foward to help you steer into the corner. It's ever so slight, but it does work.
Also remember that most systems designed for old cars like ours are compromise systems. Most of them use existing holes and mounting points, which is good for the user but may or may not compromise the performance of the unit. The original suspension was such a case - it is designed to fit the existing chassis, and it is designed for a balance of comfort and performance.
Is it better than the original style suspension? Really depends on what you plan to do with the car. 4 link, 4 bar, torque arm, IRS, leaf springs, they all have good and bad points about them. The best one for your car depends on what you wwant to do with it.