I'm new here, so I thought I'd share. I did this last spring, it was the first real mod (besides the mp3 player and industrial-strength bike rack) that my `88 got.
The kit was $350 from Street Beat Customs in Pheonix. If you've never cut a big friggin' whole in your car, I highly recomend it. Just measure about 25 times, grab the sawzall and cut. The kit I got measures 40" by 35", or something like that. I chose this size specifically so it'd fit niclely between my bike-carriers and load bars.
Let me make this clear: This roof does not leak ever, period. Well, unless you point a hose at the seams, but hell, I don't wash my car. With the fairing on the roofrack it's very quiet too, even at speed.
I placed the rag starting about where the dome light is (was). This way I still have actual roof over my head. This is good because: 1) If it starts raining, only the dog gets wet. 2) If it's brutally hot, you're still sitting in the shade. This is key here in the desert. 3) There's no way I could get a pipe lit at highway speed otherwise. Also, I sleep in my Roo alot, so having it in the back means I can look at the stars.
The height of the roof is perfect for hanging out the top limo-style, or perhaps a turret mounted .50 cal. Hmmm....
I did the trim with 1/8" aluminium, the final product is very clean. Wasteland thought it was a rare factory option when he first saw it.
Blue skies outside, blue dogs inside:
Anyway, if your car has a roof, this is definetly the coolest thing you can do with it.