OK. Well on the 4Runner this will not get you much as the top of the strut is bolted to the frame which is already very rigid. The reason why they put strut bars on cars are because they use unibody and the area in the fender the top of the strut bolts into is not that rigid. So under severe stress (hard cornering) the fender area with strut actually flexes. Where the strut bolts to the frame the flex is minimal to none on the 4R, so reinforcing it will buy you basically nothing.
To improve the handling on the 4R you probably want to look at lower profile tires, as the sidewall of the tire is what flexes the most during hard cornering. This will give the sloppy feel. Perhaps look at 18" wheels with 265/60 tires on it, this shouldn't affect your ride quality that much but improve your handling if you can get a tire with a firmer sidewall.
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