Rear window mod

[78chevydoc]

I have a 78 chevy pickup that I want to put a power rear window in.One like in a suburban, I seen this done before, and it was a very cool mod.I make a channel for the windo to go up and down but I need a way for it to move back at the top make a seal for weather tightness and to make a smooth profile to the body. I have run out ideas so why use pool of the forum for ideas?