I used part of the dash side vents for tweeters & 5.25" in the doors:
http://www.flickr.com/photos/28301891@N03/sets/72157605998819075
Very happy with results.

Todd
91 Weekender

Date:    Tue, 6 Apr 2010 08:20:51 -0700
From:    Alistair Bell <albell@SHAW.CA>
Subject: Re: Stereo Upgrade Project

Don't forget the approach of putting tweeters behind stock speaker
grill at top of door and midrange elements at foot of door. Previous
owner did that on my '86 syncro, Boston acoustic speakers, crossover
boxes on each side tucked into air channel just forward of door in
frame.

alistair
'86 syncro 7  passenger
'82 westy, diesel converted to gas in '94
http://www.members.shaw.ca/albell/
http://shufti.wordpress.com