Welcome to the bolt.
Have you ever done ANY metal work? If the answer is NO then doing a top chop is not the place the start. You WILL stand a very good chance of ruining your truck. There is more to doing a chop than cutting out 3" of the side pillars. You will need to also cut the door moldings and have special glass cut which is more difficult on the 54 with the one-piece windshield as that glass is not cheap to begin with. It would be much easier in that area if you were using a 53 or older cab with the flat glass.
My suggestion is do not do it.
