Exactly how did the sway bars attach to the body? My kit came with a very short bolt and 3 bushings (per side) which ran through the floor pan and reinforcement plates. The bolt itself is the endlink, and while it might be prone to more rigidity than longer endlinks, the bushings should still allow it to flex both laterally and front-to-back. (The floor pan/reinforcement plate acts as the pivot point.)

It sounds as though you were able to use them to anchor the rear end sufficiently without the panhard bar, so I must admit that I am curious as to how yours were set up.

My endlinks definitely allow for movement, but to make mine fit properly with the Ford rear-end, I had to lower the mounting position on the axle. I then replaced the endlinks with longer bolts and an extra bushing on each side (so that I could lower it the same distance at the body mounting positions, allowing the bar to seat neutrally in the bushings when the car is at rest).