My Duster has a leaf-link in it, but it differs a bit from what you have there. My upper housing bracket has 2 holes and the front is a modified stock framerail. The car doesn't have near the tire you do and 60'd in the 1.36-1.38 range at Norwalk, 1.40 everywhere else with a tired ole motor at 3150#.

As mentioned, I would address some other things before changing the suspension.

Good Luck