I've had HD Jeep springs. Trailmaster 4" that broke the frame at 3 spring perches. And now OME YJs with shackle reverse. The axle actually goes up and down. Great on the highway and pull the sway-bar disconnects and great on the trail.
YJ springs with a spring over if offroad performance is important to you, but be prepared to install a traction bar in the rear. If you just want the appearance and not too concerned about the axles moving, use 4" YJ springs under the axles.
No 79s did not have a 'track bar'. It may have had a sway bar. A traction bar is not the same as a track bar. A traction bar helps to eliminate wheel hop common with a spring over.