Leaking rear window

[feller]

Im the proud new owner of a 1999 Silverado 2500, with 193,xxx miles. Also I've inherited all of the 20 year old problems that go with it. First thing that needs to be done is getting the rear window to stop leaking. It has a rear slider that looks to be aftermarket, i say this because it has a frame and the po put silicone caulking around it (ironically this isn't working, if it ever did). I know that the original windows didn't have frames and used a urethane adhesive, but I don't think I've ever seen a rear slider, if i have i never paid any attention to it.

So, who has a rear slider, can I see pictures of it, was there a factory option for one, and can i make it seal?

I am 100% sure it isn't the slider that is leaking, its poor sealing where the urethane goes.

Also it's been leaking long enough to rot the passenger side floor (under the carpet) and long enough to make it smell funky (I thought the smell was from the old man who owned it,WRONG!)
any help is appreciated