Yes installing a 5.0 lever can make the 1-2 shift firmer (as long as the rear servo releases real fast) but it may also cause it to overlap (bind up) on the 2-3 shift. Personally I wouldn't give you .01$ for a 5.0 lever. Taken too many out of transmissions that guys installed that caused problems, even to the point of burning up the high clutches. A 3.8 lever will generally give you a plenty firm shift without causing bind up.