"Old fashioned ladder bars" can't be put on a car with leaf springs unless you also put a floating mount on the axle. Otherwise the ladder bars and leaf springs will bind, as they move in different arcs. The slide link system from your link looks like it should work ok, but I've never seen one in person.
What you need to do for traction depends a lot on what kind of power you are putting to the rear tires. Super Stock leaf springs work really well, since the front segment of the spring accomplishes the same thing that the slide link system does, although you can't change settings on the leaf springs. Basically, the rear suspension tries to lift the body of the car when the axle twists due to torque and plant the rear tires to the pavement. You can watch the body of the car rise a few inches at the rear wheel at launch if you look at it from the side, unlike the brand C cars that tend to squat in the rear. Make sure you also have longer rear shocks as well, since by raising the body, you extend the shocks, and can hit the end of the shocks' range of travel, which will cause you to lose traction. I also added 90-10 front shocks on my car to help the front end come up quicker to aid in weight transfer.
