Get the 1/4" butyl tape.
Make sure that, after you get the window out, you clean everything up. Make sure the window is nice and clean (I scraped it with a razor, used Windex on it, then acetone), and clean all of the butyl out of the channel in the body. If you have rust in there, this would be a very good time to fix it or at least halt its progress.
The tape gets stickier with heat. You can put the window out in the sun to warm it up so the tape will adhere more effectively. I also used a hair dryer (I don't own a heat gun) to heat the tape once I pressed it into the channel on the body.
I used the seats as clamps to hold the window in. Some folded-up towels between the back of the headrest and the window, and you can slide the seat back far enough that the towel and seat combo will hold the window. I also rigged up something with a bar clamp and some wood blocks for the top of the window. I let it sit overnight (or maybe for another day after that??) to really set up.
--DD
------------------
Pelican Parts 914 Tech Support
A few pics of my car:
http://www.pelicanparts.com/gallery/Dave_Darling