Take off that sway bar and go check if it flexes, I bet it will. Also, since it's an 85 I imagine it has push pull steering? This will limit flex as well.
As far as springs, I like ruf and Chevy 63s in the rear. But if you want to buy a spring theres trail gear and a few other places. But I'd suggest a 3 inch spring instead of 4, you'll still be able to clear 35s and 37s if you trim.
