Lowered vehicles and a smooth ride simply don't go together. Pick one- - - - -normal ride height and a smooth ride, or lowered and rough, and stick with your choice. You're going to need more suspension travel than the lowered stance can provide. Hopefully, you'll be able to raise the ride height and retain enough steering and suspension geometry to have a good ride and good handling, but those things really need to be designed into the original build. Most vendors who sell round track race car components can supply coil springs for the front to provide the proper weight distribution. If you're still running rear leaf springs, the weight carrying capacity can be altered for a smoother ride, as long as there's enough suspension travel to allow for some suspension movement without bottoming out on bumps.
Jerry