Before you make any cuts on the car, put some X-braces in the car, at least two going from left to right so that the bottom portion of the car doesn't move around on you when you cut the roof off. I usually use 1" square tubing tack welded to the inside of the body. On an A I would reccomend one between the rear of the door jambs, and another just aft of the side window openings. Chopping an A is not that difficult as most everything moves straight down. Also, make a cardboard template of the section you are cutting out so that your cuts are the same from side to side.