This could take a while to explane, I'll give a condensed version as i'm sure more people will post info as well.
The comp you may be thinking of is \"Gene Berg ent\" or Bergs as we call it. They make the 5 speed conversion and a few forum members have them. The most common confusion is that people thing your getting a extra gear. This is not really true as what your doing is making a closer 1-4 gear set then instaling a stock 4th in the 5th location giving good track times and hwy drivability.
You can instal a Porsche 911 trans, a 901 is the easy one to instal. A 914 has a side shift 5 speed and is too much work. a Porscg 911 915 trans will also work but you need to find one with the correct ratio as your motor may not have enough power to use it.
Yes you can convers a 914 2.0L into a beetle but it can be costly and you still only end up with 100hp or so.
Build a nice 2.0l T1 motor and a good t1 3;88 trans 4speed or Berg 5 and you should be happy, if not go towards the 901 or 915 (the last two can be expensive and a lot needs to be done to make them work.
Geoff.