Springs will make more difference than struts but bad struts will delete some of the improvement. You need to find car in JY that has F41 on the code chart in trunk. Buy the springs and struts in one piece. Buy the bars. Big difference. I am in process of putting older F41 on my 90 Regency. The rear springs and bar is in and that really made a difference. I cant wait to tighten up the front too. You need to drop tie rod on one end I believe to get front sway out and in.
You could find F41 in SSEi, LSS and if you see a LeSabre with nicer aluminum wheels it may have the handling package as well. You need to see F41 on the options sticker. Go by that not diameter. Temper has alot to do with springs too. There is no diameter difference in the rear springs I just removed from my Regency to the ones I put in.
86 LeSabre coupe, 90 Regency, 90 Ciera Cruiser and the 97 LSS have a new stable mate............06 G6 GTP coupe, white with taupe & black interior