if you're looking for something that will fit in a stock dash, Kenwood still makes one. I have their KRC3006 am/fm/casstte deck (it fits in the dash and comes with a faceplate that also fits, is available from the repro houses) and thier 10 disk remote changer in the trunk.
I got a sub in the trunk, which works well, but regular speakers don't, you can't hear them with the top down and the high freq's get severely muffled.
Check the convertible forum at
www.camaros.net, speakers in ragtops is a matter of much discussion their. One member managed to get 5 1/4" drivers into the rear side panels, just below the folded down top frame. Another did a really slick install in the kickpanel vent. Other have even put tweeters in the astro vent tubes!