@Delta VS Another Data Point: 97FZJ80 with Slinky Intermediates and a 5” difference between axle and frame panhard mounts - I had to grind down the 3” bracket, it was touching the spring and interfering with alignment of bolt holes. Need to update the design with less of a spine.
FWIW - I have adjustable upper arms and they were set to level the pinion.
I think I just discovered this with my Slinky Intermediates as well. I should have read this whole thread before installing. No adjustable control arms, in my case.