Have anybody here in this forum ever top chopped a 53-54 Chevy Hardtop, walking around mine to find the right place to cut.
post some pics of your car - need to do lots of measuring, supporting inside of car, etc before just making a cut. best to plan on lowering windshield and rear glass into body. if you just cut may never get glass to fit - why there are plenty of ads out there for chopped cars that turn out to be botched roof chops. do a long search here for threads on doing a chopped roof. post pics of Chevys that you have seen that you like the way the chopped roof looks.
I did search thru google some time back and came up with an article featuring chopping a 53 Hardtop. Pictures showed dropping the the rear window channel into the package tray. It is a lot of help in picturing what has to happen. Myself, I have chosen to change the whole rear part of the roof and window to a Styleline window.