You just need a link type traction bar with the leafs to keep the spring from winding up. Lots cheaper/easier than installing ladder bars, and won't affect ride as much. You could use slapper bars if budget is a major concern, but a 4x4 type traction bar isn't much more or much harder to install.
On a smooth road ladder bars will ride as good as any other suspension. Even a straight front axle rides and handles good on smooth pavement. When the going gets rough so does the ride though, since one wheel can't move far without affecting the other. All live rear axles are that way to a degree, but ladder bars will restrict movement more and decrease ride comfort ON ROUGH ROADS. The longer the bars the better -- no less than 30". Shorter will ride rougher.