Another good source of info is Tom Wilson's "How to Rebuild Your Volkswagen Air-Cooled Engine". He even addresses 914s specifically!
There's one very confusing bit in his book, though. It's about timing the cam gear to the crank gear--the same paragraph talks about both Type I and Type IV, which use rather different procedures. Apart from that, he has a lot of very good info about what "needs" to be replaced and how everything gets done. Even the machining!
Rimco
http://www.rimcovw.com does good work. Headflow Masters (used to be
http://www.audiracvw.com or
http://www.audiracvws.com but now those don't come up for me) has also been recommended by Jake in the past. He uses someone else now, and recommends them.
--DD