A Z3 shifter will reduce your throw by approximately 20% i think. Dont qoute me on the precise amount but it will reduce your throw. I know that for a fact. Most people just slap it in and call it good. But i personally dont like the angle it puts the shifter at. It moves it slightly foward so i bent the one i used using a blow torch and a vise to get it where i like it.
For a weighted selector rod which would give you smoother shifts you can wrap solder around the selector rod like a coil and simply tape the ends.
Works like a charm.