Are you thinking of the Cal Track bars?

Conventional "slapper" traction bars only screw up the way Mopar springs are supposed to work.

There's a new type of device similar to a traction bar, but it actually creates almost a 4-link action and works WITH the springs... can't remember the vendor that makes it right off. There was a write up in a recent 'Muscle Car Enthusiast' magazine, and I'd first heard about it 4-5 years ago. It has a boxed bracket that mounts around the front spring hanger, and then a plate that mounts under the axle U-bolts. An adjustable linkage attaches the plate to the boxed bracket, and allows you to adjust the amount of pre-load on the link, which counteracts the tendency of the nose of the differential to rotate upward on a hard launch.