We removed the old front speakers, then used a dremel with a cutting blade
to cut the threaded area off of the speakers (taking the old speakers with
it).  This created a flat speaker cover.  Taped cover over our new speakers
and then drilled four holes though the edges, used a bigger drill bit from
the front to create a little bit of a 'counter sink'.  Installed our new
speakers by using nice black trim screws though the cover, through the door
panel, through the speaker and then into screw clips.  Worked perfectly and
looks factory except for the exposed screw heads.

In the back we just discarded the old  ceiling mount speakers (after
destroying the housing trying to get them apart), a nice set of small box
speakers with metal brackets bolted into the factory mount holes.  Added
benefit is these are now dual speakers.

Just an AMAZING difference in sound quality, total cost was about 50 CDN and
a couple hours of my time.

Richard Lynch
85 Vanagon