Hi,
Save yourself some time and don't even try to install it. I've never been able to get one of those things adjusted to the point where you can get all 4 gears AND reverse (with lockout). Usually you have to enlarge the slot in the housing that holds the shifter.(the thing that's bolted to the floor and the shifter comes out of it), and it still won't work 100%.
Instead, buy (even the cheapest ones) a complete shifter. It has the shorter throw built in and usually they have a better reverse lock-out than the stock shifter. Check around on the internet. Every mail order VW parts house sells them. They "bolt in" and are much easier to adjust.
The only compromise is that they don't look like VW or Porsche parts. I have one in my Speedster. It the Hurst style short shifter. It came with a "black ball" gear shift knob. I just used my stock shift knob (had to made a threaded bushing). Now it doesn't look so obvious, like something that belongs in a Chevy.
Bottom line is that they work, and they shorten the shift throw, have a better reverse lock out and have a more positive feel.
Greg B.