It is indeed possible. Try to get as late as you can, because the latches on the very earliest ones are a little different. Get the whole framework, which includes the front window track. Be very careful to get one that has not rusted out the pivot at the bottom. When they wear out, the post in the bottom begins to rotate in the frame of the movable glass, and this is fatal. It will never stay open. Pass on any window that does not show good firm connection of the post to the glass. It should turn smoothly against the spring that's below the outer frame only.
Once they're in, you can get a good way toward making them leakproof if you take some time. First of all, make sure all gaskets are lined up right. If one is folded, unfold it and close the window on it, and eventually it will retrain. Coat the sealing surfaces very lightly with silicone grease (silicone only, the sort of thing that does not react with rubber) and this will reduce leaks greatly too. Finally, you can adjust the seating of the window a little by loosening the phillips screw in the top pivot, and moving the whole glass a little. If the lower pivot is loose, you can take it apart by removing the tiny roll pin that holds the latch on. Make sure you don't lose the wavy washer under the latch. The post is hollow, and inside it is a phillips screw that holds it to the glass.
Some people hate the movable vents, but I loved them, and moved a set from my 87 to the 95. Unbeatable if you lack or do not like the air conditioner.
