Shorter throw is achieved by lowering the shifter ball on the bottom of the shifter in the socket on the end of the shifter rod. This cost-effective kit gives you not only a shim (top arrow) that sits on top of the conical bell on the shifter to lower it somewhat, but it also gives you a cast aluminum spacer to put under the shifter bell cover to raise the whole mechanism back up (so that the side stops/reverse stop tangs will be aligned and not give any sloppiness or binding). So yes, it giveth some and then it taketh away some.
IMHO, it may provide some shortening of throw but I really doubt that it would be significant enough to really feel it and appreciate. But at the price, it would be worth a try.
Again, just my 2 cents worth. I hope it does give you some good results if you try it. Keep us informed.