The problem with leaf springs are that you can only get them in one linear spring rate. A soft spring will ride nice, but wrap up under hard acceleration or braking. A harder spring will work great on the track, but knock your teeth out on the street.

Personally, I think one of the best designs for the Mustang leaf spring is from Maier Racing. They have a leaf spring that actually replaces the need for your traction bars. Most leaf springs on the market are to thin in the front half giving inadequate control of the suspension ( Wheel Hop) do to being to week. Maier springs have two extra half leafs that go all the way to the front of the spring along with the rest of the leafs. These leaf are also held together by quarter inch thick riveted clamps that won't rip off under heavy loads. This design takes care of the spring wrap up which is half of the problem creating wheel hop. The result is a decent ride while still having the strength to handle high-horsepower and drag racing.

You can get a lot of different configurations for the rear leafs. I have a set of Global West specials that made to solve some of the problems with wheel hop and other issues with the Mustang leafs. They are also fitted with spherical bearings instead of bushings. Costly, but worth it. Also depending on your application you can move the rear or front mount points up to get better accel or decel performance. You may also be able to acomplish the same with some of the Mid or Reverse Eye springs, but I have never used them so can't say about quality. Another area of importance is the shackles, the rubber is the worst, urethean is not quite as bad, but the best that I have seen are the ones from Global West. Contact the folks like Maier, Global West you should get enough info. If your drag racing that will also be a different application then Road Racing due to the nature of the loads placed on the springs. Watch Pinion angle with any new style springs.