rear sway bar?

As a guy who has installed both the Hellwig and Firmfeel, the Hellwig is a better installed design. The firmfeel frame mounts go right where brake line(drivers side) and fuel/return line(pass side) go, so they need to be moved. When I did the FF ona 70 dart, I had to cut the fuel lines and add braided steel. The Hellwig is a fantastic setup.

Keep in mind you need the bigger front bar they make to have their rear bar. Having front/rear bars the same size is not a good idea.

Dave might chime in and let you know why.