> What are the largest speakers I can easily fit in the stock locations.

David,

I was able to install Infinity 3.5'' speakers INSIDE the plastic factory
grilles.  I pried out the factory speakers, bent back the tabs on the new
ones, pressed them into place (they fit very snugly and securely), and
used a heavy-duty silicone compound to seal them in place.  Now I have
great sound, for 3.5'' speakers anyway, and everything looks stock.  My
10'' 300 watt sub in a small q-logic enclosure behind the back seat
provides all the boom I need.

I've read about people using rear window cranks from a Golf Cabriolet to
clear aftermarket speakers.

Chris S.
'85 Wolfsburg Westy "Camel"
http://www.knology.net/~vw/dadada.jpg