I also replaced my 4x6 rears with 6" subs. The pics are on my thread.
http://www.gmt400.com/forum/showthread.php?12725-Shelbys-Z71&p=276638&viewfull=1#post276638
Much better sound. Looks wise I coulda done a better job. Need to finish it out soon.
yea, i seen those pics... i was meaning to ask u (cuz i like a clean, factory look) would it have been possible to mount the speaker to the metal behind the trim, so that the trim could have been reused?