Possible? No. Take the window out. It is NOT difficult.
It is a neoprene gasket and should have no caulking or adhesive on it at all.
With the glass out it is a simple easy process.
I don't think you can get the new pickup in the tank unless you go through that window opening.
It goes in the tank ONE way and you can not bend the thing to force it in.
The stainless trim comes off first and all in one piece, then you can pry the rubber gasket with a putty knife to get it started and pull it out with you hands.
If you look at the window from inside of the engine compartment you will clearly see the inside flange of the rubber gasket.
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